Chemistry Level) (CIE) Paper 3

This question paper consists of 7 printed pages and 1 blank page.

SP (NF) S25943/2© CIE 2002 [Turn over

CAMBRIDGE INTERNATIONAL EXAMINATIONS

General Certificate of Education Advanced Level

CHEMISTRY 9701/3PAPER 3 Practical Test

MAY/JUNE SESSION 20021 hour 15 minutes

Candidates answer on the question paper.Additional materials:

As listed in Instructions to Supervisors

TIME 1 hour 15 minutes

INSTRUCTIONS TO CANDIDATES

Write your name, Centre number and candidate number in the spaces at the top of this page.

Answer all questions.

Write your answers in the spaces provided on the question paper.

INFORMATION FOR CANDIDATES

The number of marks is given in brackets [ ] at the end of each question or part question.

You are advised to show all working in calculations.

Use of a Data Booklet is unnecessary.

Qualitative analysis notes are printed on pages 6 and 7.

FOR EXAMINER’S USE

1

2

TOTAL

CandidateCentre Number Number

Candidate Name

http://www.xtremepapers.net

2

9701/3/M/J/02

1 FA 1 is a metal carbonate, XCO3.FA 2 is 2.00 mol dm–3 hydrochloric acid, HCl.

The carbonate and acid react according to the following equation.

XCO3(s) + 2HCl (aq) → XCl2(aq) + CO2(g) + H2O(l)

The enthalpy change, ∆H, for this reaction is –59.5 kJ mol–1.

You are required to determine the temperature rise when a known mass of the solidcarbonate, XCO3, is added to an excess of hydrochloric acid and to use your results tocalculate the relative atomic mass, Ar, of the metal X.

Experiment 1

(a) Weigh the weighing bottle.Add between 3.30 g and 3.50 g of FA 1 to the weighing bottle and accurately weigh thebottle and contents. Record this mass in Table 1.1 below.

(b) Place the plastic cup inside a 250 cm3 beaker. Using the measuring cylinder providedadd 50.0 cm3 of hydrochloric acid, FA 2, to the plastic cup.

Measure the initial temperature of the acid in the cup and record this in Table 1.2 at thetop of page 3.

Empty the contents of the weighing bottle into the acid and stir gently with thethermometer. Record the maximum temperature achieved when the solid has reactedwith the acid in Table 1.2 at the top of page 3.

Reweigh the empty bottle, which may contain some residual FA 1 and record this valuein Table 1.1 below.

Experiment 2

(c) Repeat parts (a) and (b) using a clean dry plastic cup, fresh FA 1 and fresh FA 2.

Table 1.1 Mass of FA 1.

[2]

(d) Calculate the average of the two masses of FA 1 used in Experiment 1 and Experiment 2.

ForExaminer’s

Use

Expt 1 Expt 2

Mass of weighing bottle + FA 1 / g

Mass of weighing bottle + residual FA 1 / g

Mass of FA 1 added to acid / g

3

9701/3/M/J/02 [Turn over

Table 1.2 Temperature changes.

[1]

Accuracy [8]

(e) Calculate the average temperature rise for Experiment 1 and Experiment 2.

(f) Using the average temperature rise from (e) calculate the amount of heat produced bythe reaction in the plastic cup.(Assume that 4.3 J are required to raise the temperature of 1.0 cm3 of the solution by 1.0 °C)

[1]

(g) Using your answer to (f) and the ∆H value for the reaction calculate how many moles of FA 1 have reacted.

[1]

(h) Using the average mass of FA 1 calculated in (d) and your answer to (g) calculate therelative atomic mass, Ar, of the metal X.[Ar; C, 12.0; O, 16.0.]

[2]

[Total 15]

ForExaminer’s

Use

Expt 1 Expt 2

Maximum temperature achieved / °C

Initial temperature of FA 2 / °C

Temperature rise / °C

2 The solution FA 3 contains one cation and two anions from the following list: (Al3+, NH4+,

Ba2+, Ca2+, Cr3+, Cu2+, Fe2+, Fe3+, Pb2+, Mg2+, Mn2+, Zn2+; CO32–, CrO4

2–, Cl–, Br–, I–,NO3

–, NO2–, SO4

2–, SO32–.).

In all tests, the reagent should be added gradually until no further change is observed,with shaking after each addition.Record your observations and the deductions you make from them in the spacesprovided.Your answers should include

• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.

You should indicate clearly at what stage in a test a change occurs, writing anydeductions you make alongside the observations on which they are based.

Marks are not given for chemical equations.No additional or confirmatory tests for ions present should be attempted.

Candidates are reminded that definite deductions may be made from tests wherethere appears to be no reaction.

Test Observations [5] Deductions [4]

(a) Place 4 cm depth ofFA 3 in a boiling-tube and add thecontents of the tubelabelled sodiumcarbonate

(b) Place 1 cm depth ofFA 3 in a test-tubeand add an equaldepth of dilute nitricacid.

Add aqueousbarium nitrate.

4

9701/3/M/J/02

ForExaminer’s

Use

5


Summary

The cation present in FA 3 is ……………

The anions present in FA 3 are …………… and ……………[1]

[Total 10]

ForExaminer’s

Use

Test Observations Deductions

(c) Place 1 cm depth ofFA 3 in a test-tubeand add an equaldepth of dilute nitricacid.

Add aqueous silvernitrate,

followed by diluteaqueous ammonia.

(d) Place 2 cm depth ofFA 3 in a test-tubeand add dilutesodium hydroxide.

(e) Place 2 cm depth ofFA 3 in a test-tubeand add diluteaqueous ammonia.

(f) Place 2 cm depth ofFA 3 in a test-tubeand add dilutehydrochloric acid.

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9701/3/M/J/02

QUALITATIVE ANALYSIS NOTES

[Key: ppt. = precipitate]

1 Reactions of aqueous cations

[Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)

chromium(III),Cr3+(aq)

zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)

manganese(II),Mn2+(aq)

reaction with

NaOH(aq) NH3(aq)

white ppt.soluble in excess

ammonia produced on heating

no ppt. (if reagents are pure)

green ppt.insoluble in excess


white ppt. with high [Ca2+ (aq)]

pale blue ppt.insoluble in excess

blue ppt. soluble in excessgiving dark blue solution


white ppt.insoluble in excess





grey-green ppt. soluble in excessgiving dark green solution

red-brown ppt.insoluble in excess

off-white ppt.insoluble in excess



no ppt.

no ppt.

grey-green ppt.insoluble in excess


ion

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9701/3/M/J/02

2 Reactions of anions

3 Tests for gases

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

CO2 liberated by dilute acids

yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

gives white ppt. with Ag+(aq) (soluble in NH3(aq));gives white ppt. with Pb2+(aq)

NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq));gives white ppt. with Pb2+(aq)

NH3 liberated on heating with OH–(aq) and Al foil

SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq));gives yellow ppt. with Pb2+(aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excessdilute strong acid)

gas test and test result

turns damp red litmus paper blue

gives a white ppt. with limewater(ppt. dissolves with excess CO2)

bleaches damp litmus paper

‘pops’ with a lighted splint

relights a glowing splint

turns potassium dichromate(VI) (aq) from orange to green

ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2

sulphur dioxide, SO2

8

9701/3/M/J/02

BLANK PAGE

This document consists of 8 printed pages and an insert.

SP (NF/SLC) S39116/3© CIE 2003 [Turn over

CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education

Advanced Subsidiary Level and Advanced Level

CHEMISTRY 9701/03

Paper 3 Practical TestMay/June 2003

1 hour 15 minutesCandidates answer on the Question Paper.Additional materials: As listed in the Instructions to Supervisors.

Insert

READ THESE INSTRUCTIONS FIRST

Write your details, including examination session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen in the spaces provided on the Question Paper.You may use a pencil for any diagrams, graphs, or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualtitative Analysis notes are provided on pages 7 and 8.An Insert is provided for question 1.

Centre Number Candidate Number Name

For Examiner’s Use

If you have been given a label, look at thedetails. If any details are incorrect ormissing, please fill in your correct detailsin the space given at the top of this page.

Stick your personal label here, ifprovided.

1

2

TOTAL

SESSION

LABORATORY

www.xtremepapers.net


2

9701/03/M/J/03

1 FA 1 is an aqueous solution of sodium thiosulphate, Na2S2O3.FA 2 is dilute hydrochloric acid, HCl.

When a solution of sodium thiosulphate is mixed with hydrochloric acid a reaction takesplace and a fine suspension of solid sulphur is formed in the solution.

Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l)

If a beaker containing the reaction mixture is placed over a marker, in this case an insert ofprinted text on a piece of paper, the sulphur as it forms slowly hides the marker from view.

If the depth of solution in the beaker is kept constant the marker will always disappear whenthe same amount of sulphur has been formed.

(a) Use a 50 cm3 measuring cylinder to place 50.0 cm3 of FA 1 into a 250 cm3 beaker.Measure 5.0 cm3 of FA 2 into the small measuring cylinder.

Dry the outside of the beaker containing FA 1 and place it over the printed text on theinsert sheet.Pour the 5.0 cm3 of FA 2 from the measuring cylinder into the beaker and at the samemoment start a stop-clock or note the time on a clock with a seconds sweep hand.

Swirl the beaker to mix the solutions thoroughly and place back over the insert. Theinsert should then be viewed from above so that the text is observed through the depth ofthe solution.

Stop the stop-clock or note the time when the printing on the insert is just nolonger visible.

Record the time to the nearest second in Table 1.1.

Empty and rinse the beaker. Repeat the experiment placing the volumes (shown inTable 1.1) of FA 1 and water in the beaker and then adding FA 2.

Table 1.1

Calculate (correct to one decimal place) for each experiment. [1]

Accuracy [6]

1000time

You are to use this reaction to investigate how the rate of reaction between sodiumthiosulphate solution and hydrochloric acid changes as the concentration of thesodium thiosulphate solution is varied.

ForExaminer’s

Use

Expt volume of volume of volume of timeFA 1 water FA 2

/ cm3 / cm3 / cm3 / s / s–1 × 103

1 50.0 0.0 5.0

2 40.0 10.0 5.0

3 30.0 20.0 5.0

4 25.0 25.0 5.0

5 20.0 30.0 5.0

6 15.0 35.0 5.0

1000time



3


(b) Explain why is a measure of the rate of reaction.

..........................................................................................................................................

......................................................................................................................................[1]

(c) Plot a graph of against the volume of FA 1 (sodium thiosulphate)

[5]

0 10 20

volume of FA 1 / cm3

1000

/tim

e s–1

x 1

03

30 40 50

1000time

1000time

ForExaminer’s

Use



(d) How is the rate of reaction related to the concentration of sodium thiosulphate solution?

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(e) Explain why the total volume of solution used in each experiment is kept constant.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total 15]

4

9701/03/M/J/03

ForExaminer’s

Use



5


2 FA 3 is a mixture of two solids, FA 4 which is soluble in water and FA 5 which is insoluble inwater.

Tip the solid FA 3 into a boiling tube, add distilled water until the tube is half full, stopper andshake for about 30 seconds. Filter the mixture and retain both the filtrate and the residue.

In all tests, the reagent should be added gradually until no further change is observed,with shaking after each addition.Record your observations in the spaces provided.

Your answers should include• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.

You should indicate clearly at what stage in a test a change occurs.


Tests on the Filtrate containing FA 4

ForExaminer’s

Use

Test Observations [4]

(a) To 2 cm depth of the filtrate in a boiling-tube, add 2 cm depth of aqueous sodiumhydroxide,

then carefully warm the solution.

(b) To 1 cm depth of the filtrate in a test-tube,add 1 cm depth of aqueous lead nitrate.

(c) To 2 cm depth of the filtrate in a test-tube,add 2 cm depth of aqueous hydrogenperoxide followed by 1 cm depth of dilutesulphuric acid.



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9701/03/M/J/03

Tests on the Residue, FA 5

Use the information in the Qualitative Analysis Tables on pages 7 and 8 to identify the ionspresent in FA 4 and FA 5.

The ions present in FA 4 were .............................................

What evidence has lead you to deduce the ions present in FA 4?

..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................



..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................[3]

[Total 10]

ForExaminer’s

Use


(d) Transfer the solid residue from the filterpaper to a boiling-tube and add aminimum quantity of dilute hydrochloricacid to dissolve the solid.

Divide the solution into two parts and useone part for each of the following tests.

To one part add aqueous sodiumhydroxide.

To the other part add dilute aqueousammonia.



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9701/03/M/J/03





aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion



8

9701/03/M/J/03


3 Tests for gases

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2




This document consists of 8 printed pages and an insert.

SP (NF/SLC) S39116/3© CIE 2003 [Turn over

CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education


CHEMISTRY 9701/03


1 hour 15 minutesCandidates answer on the Question Paper.Additional materials: As listed in the Instructions to Supervisors.

Insert


Write your details, including examination session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen in the spaces provided on the Question Paper.You may use a pencil for any diagrams, graphs, or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualtitative Analysis notes are provided on pages 7 and 8.An Insert is provided for question 1.





1

2

TOTAL

SESSION

LABORATORY


2

9701/03/M/J/03

1 FA 1 is an aqueous solution of sodium thiosulphate, Na2S2O3.FA 2 is dilute hydrochloric acid, HCl.

When a solution of sodium thiosulphate is mixed with hydrochloric acid a reaction takesplace and a fine suspension of solid sulphur is formed in the solution.

Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l)

If a beaker containing the reaction mixture is placed over a marker, in this case an insert ofprinted text on a piece of paper, the sulphur as it forms slowly hides the marker from view.

If the depth of solution in the beaker is kept constant the marker will always disappear whenthe same amount of sulphur has been formed.

(a) Use a 50 cm3 measuring cylinder to place 50.0 cm3 of FA 1 into a 250 cm3 beaker.Measure 5.0 cm3 of FA 2 into the small measuring cylinder.

Dry the outside of the beaker containing FA 1 and place it over the printed text on theinsert sheet.Pour the 5.0 cm3 of FA 2 from the measuring cylinder into the beaker and at the samemoment start a stop-clock or note the time on a clock with a seconds sweep hand.

Swirl the beaker to mix the solutions thoroughly and place back over the insert. Theinsert should then be viewed from above so that the text is observed through the depth ofthe solution.

Stop the stop-clock or note the time when the printing on the insert is just nolonger visible.

Record the time to the nearest second in Table 1.1.

Empty and rinse the beaker. Repeat the experiment placing the volumes (shown inTable 1.1) of FA 1 and water in the beaker and then adding FA 2.

Table 1.1

Calculate (correct to one decimal place) for each experiment. [1]

Accuracy [6]

1000time

You are to use this reaction to investigate how the rate of reaction between sodiumthiosulphate solution and hydrochloric acid changes as the concentration of thesodium thiosulphate solution is varied.

ForExaminer’s

Use

Expt volume of volume of volume of timeFA 1 water FA 2

/ cm3 / cm3 / cm3 / s / s–1 × 103

1 50.0 0.0 5.0

2 40.0 10.0 5.0

3 30.0 20.0 5.0

4 25.0 25.0 5.0

5 20.0 30.0 5.0

6 15.0 35.0 5.0

1000time

3


(b) Explain why is a measure of the rate of reaction.

..........................................................................................................................................

......................................................................................................................................[1]

(c) Plot a graph of against the volume of FA 1 (sodium thiosulphate)

[5]

0 10 20


1000

/tim

e s–1

x 1

03

30 40 50

1000time

1000time

ForExaminer’s

Use

(d) How is the rate of reaction related to the concentration of sodium thiosulphate solution?

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(e) Explain why the total volume of solution used in each experiment is kept constant.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total 15]

4

9701/03/M/J/03

ForExaminer’s

Use

5


2 FA 3 is a mixture of two solids, FA 4 which is soluble in water and FA 5 which is insoluble inwater.

Tip the solid FA 3 into a boiling tube, add distilled water until the tube is half full, stopper andshake for about 30 seconds. Filter the mixture and retain both the filtrate and the residue.

In all tests, the reagent should be added gradually until no further change is observed,with shaking after each addition.Record your observations in the spaces provided.

Your answers should include• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.



Tests on the Filtrate containing FA 4

ForExaminer’s

Use


(a) To 2 cm depth of the filtrate in a boiling-tube, add 2 cm depth of aqueous sodiumhydroxide,

then carefully warm the solution.

(b) To 1 cm depth of the filtrate in a test-tube,add 1 cm depth of aqueous lead nitrate.

(c) To 2 cm depth of the filtrate in a test-tube,add 2 cm depth of aqueous hydrogenperoxide followed by 1 cm depth of dilutesulphuric acid.

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9701/03/M/J/03

Tests on the Residue, FA 5

Use the information in the Qualitative Analysis Tables on pages 7 and 8 to identify the ionspresent in FA 4 and FA 5.



..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................



..................................................................................................................................................

..................................................................................................................................................

..................................................................................................................................................[3]

[Total 10]

ForExaminer’s

Use


(d) Transfer the solid residue from the filterpaper to a boiling-tube and add aminimum quantity of dilute hydrochloricacid to dissolve the solid.

Divide the solution into two parts and useone part for each of the following tests.

To one part add aqueous sodiumhydroxide.

To the other part add dilute aqueousammonia.

7

9701/03/M/J/03





aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion

8

9701/03/M/J/03


3 Tests for gases

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2


This document consists of 7 printed pages and 1 blank page.

MML 5664 4/03 S65492/2© UCLES 2004 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education


CHEMISTRY 9701/03


1 hour 15 minutesCandidates answer on the Question Paper.Additional Materials: As listed in the Instructions to Supervisors.


Write your details, including examination session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen in the spaces provided on the Question Paper.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualitative Analysis notes are provided on pages 6 and 7.



LABORATORY

SESSION

1

2

TOTAL





© UCLES 2004

2

9701/03/M/J/04

ForExaminer's

Use1 FA 1 is anhydrous sodium carbonate, Na2CO3, provided in a stoppered tube.

FA 2 is an aqueous solution of hydrochloric acid, HCl.

Acids and carbonates in solution react as shown in the equation.

2H+(aq) + CO32–(aq) → H2O(l) + CO2(g)

You are to determine the concentration, in mol dm–3, of the hydrochloric acid solution FA 2.

(a) Weigh the stoppered tube labelled FA 1 and record the mass in Table 1.1.

Table 1.1 Weighing of sodium carbonate

[1]

Transfer the contents of the weighed tube into a 250 cm3 beaker and dissolve the solid inabout 100 cm3 of distilled water.

Reweigh the tube and stopper and any residual sodium carbonate and record the mass inTable 1.1. Calculate the mass of sodium carbonate dissolved in the water.

(b) Transfer the sodium carbonate solution to the graduated flask labelled FA 3. Rinse thebeaker with distilled water several times, adding each rinsing to the graduated flask.This ensures that all of the sodium carbonate has been transferred to the flask.Make up the solution to 250 cm3 with distilled water and mix thoroughly.

Pipette 25.0 cm3 of FA 3, the sodium carbonate, into a conical flask and place the flaskon a white tile. Add a few drops of the indicator provided and titrate with FA 2, thehydrochloric acid.

Repeat the titration as many times as you think necessary to obtain accurateresults. Make certain that the recorded results show the precision of yourpractical work.

Table 1.2 Titration of FA 3 with FA 2

Indicator used: .................................................................................

[2] + [6]Summary

25.0 cm3 of FA 3 reacted with ............................. cm3 of FA 2.

Show which results you used to obtain this volume of FA 2 by placing a tick (�) under thereadings in Table 1.2.

Mass of tube + FA 1 / g

Final burette reading / cm3

Initial burette reading / cm3

Volume of FA 2 used / cm3

Mass of tube + residual FA 1 / g

Mass of FA 1 used / g



You are advised to show full working in all parts of the calculations.

(c) Calculate the concentration in mol dm–3 of the sodium carbonate, Na2CO3, in FA 3.[Ar: Na, 23.0; C, 12.0; O, 16.0.]

[2]

(d) Calculate how many moles of sodium carbonate, Na2CO3, were pipetted into theconical flask.

[1]

(e) Calculate how many moles of hydrochloric acid, HCl, have been run from the burette.

2H+(aq) + CO32–(aq) → H2O(l) + CO2(g)

[1]

(f) Calculate the concentration, in mol dm–3, of HCl in FA 2.

[2]

[Total: 15]

3


ForExaminer's

Use

© UCLES 2004



2 FA 4, which is provided in a stoppered boiling-tube, is a mixture of two solids:FA 5, which is soluble in water andFA 6, which is insoluble in water.

Add 20 cm3 of distilled water to the boiling-tube and carefully warm the mixture to dissolveFA 5. Filter the mixture and retain both the filtrate and the residue.

Carry out the following tests and identify any gases given off.

Tests on the Filtrate (FA 5)

Use the information in the Qualitative Analysis Table on page 7 to identify the anion presentin FA 5.

The anion present in FA 5 is ...................................................................................................

Which observations support your choice of this anion?

.................................................................................................................................................

.................................................................................................................................................

........................................................................................................................................... [1]

4

9701/03/M/J/04

ForExaminer's

Use

© UCLES 2004


(a) To 1 cm depth of the filtrate in a test-tube, add 1 cm depth of aqueousbarium chloride;

followed by 2 cm depth of dilutehydrochloric acid.

(b) To 1 cm depth of the filtrate in a test-tube, add 1 cm depth of acidifiedaqueous potassium dichromate(VI).Leave to stand for 1 minute.

(c) To 1 cm depth of the filtrate in a boiling-tube, add 2 cm depth of dilutehydrochloric acid.Warm the solution and identify the gasgiven off.Empty and wash away the contents of the tube at the end of this test.

(d) To 1 cm depth of the filtrate in a test-tube, add 2 cm depth of aqueousiodine.



In tests (b) and (d) the anion in FA 5 is behaving as

........................................................................................................................................... [1]

Tests on the Residue (FA 6)

Use a spatula to transfer the residue from the filter paper to a boiling tube.

Use the information in the Qualitative Analysis Table on pages 6 and 7 to identify the cationand anion present in FA 6.

The cation present in FA 6 is .................................................................................................

The anion present in FA 6 is ..................................................................................................

Which observations support your choice of these ions?

cation .......................................................................................................................................

.................................................................................................................................................

anion .......................................................................................................................................

........................................................................................................................................... [1]

[Total: 10]

5


ForExaminer's

Use

© UCLES 2004


(e) Add 2 cm depth of hydrochloric acid tothe residue (FA 6) in the boiling-tube.

Use the solution formed in this test for thefollowing tests, (f) and (g).

(f) To 1 cm depth of the solution made in test (e) in a test-tube add aqueoussodium hydroxide.

(g) To 1 cm depth of the solution made in test (e) in a test-tube add 1 cm depth ofaqueous ammonia.







6

9701/03/M/J/04© UCLES 2004

aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion



© UCLES 2004


3 Tests for gases

7

9701/03/M/J/04

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2




BLANK PAGE

University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a departmentof the University of Cambridge.

8

9701/03/M/J/04




SP (SJF3513) S81256/3© UCLES 2005 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education


CHEMISTRY 9701/03


1 hour 15 minutesCandidates answer on the Question Paper.Additional Materials: as listed in the Instructions to Supervisors.


Write your details, including practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen in the spaces provided on the Question Paper.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualitative Analysis notes are provided on pages 6 and 7.


SESSION LABORATORY




1

2

TOTAL



© UCLES 2005

2

9701/03/M/J/05

ForExaminer's

Use

1 FA 1 is a solution containing 5.00 g dm–3 of hydrated ethanedioic acid, H2C2O4.xH2O.FA 2 is a solution containing 2.37 g dm–3 of potassium manganate(VII), KMnO4.You are also provided with 1.00 mol dm–3 sulphuric acid, H2SO4.

In the presence of acid, potassium manganate(VII) oxidises ethanedioic acid;

2MnO4–(aq) + 5H2C2O4(aq) + 6H+(aq) → 2Mn2+(aq) + 10CO2(g) + 8H2O(l)

You are to determine the value of x in H2C2O4.xH2O.

(a) Fill the burette with FA 2.

Pipette 25.0 cm3 of FA 1 into a conical flask. Use the measuring cylinder provided toadd to the flask 25 cm3 of 1.00 mol dm–3 sulphuric acid and 40 cm3 of distilled water.

Heat the solution in the flask until the temperature is just over 65 °C. The exacttemperature is not important.

Be careful when handling hot solutions.

Remove the thermometer and carefully place the hot flask under the burette. If theneck of the flask is too hot to hold safely, use a folded paper towel to hold the flask.Run in about 1 cm3 of FA 2. Swirl the flask until the colour of the manganate(VII) ionshas disappeared then continue the titration as normal until a permanent pale pinkcolour is obtained. This is the end point. Record the burette readings in Table 1.1.

If a brown colour appears during the titration, reheat the flask to 65 °C. The browncolour should disappear and the titration can then be completed.

If the brown colour does not disappear on reheating, discard the solution and restartthe titration.

Repeat the titration as many times as you think necessary to obtain accurateresults.

Make certain that the recorded results show the precision of your practical work.


Summary

25.0 cm3 of FA 1 reacted with ………………. cm3 of FA 2.

Show which results you used to obtain this volume of FA 2 by placing a tick (✓) underthe readings in Table 1.1.

[7]

final burette reading / cm3

initial burette reading / cm3

volume of FA 2 used / cm3




(b) Calculate how many moles of potassium manganate(VII), KMnO4, were run from theburette during the titration.[Ar: K, 39.1; Mn, 54.9; O, 16.0.]

[2]

(c) Calculate how many moles of ethanedioic acid, H2C2O4, reacted with the potassiummanganate(VII) run from the burette.

[1]

(d) Calculate the mass of H2C2O4 in each dm3 of FA 1[Ar: H, 1.0; C, 12.0; O, 16.0.]

[3]

(e) Calculate the mass of water in the 5.00 g of H2C2O4.xH2O.

[1]

(f) Calculate the value of x, in H2C2O4.xH2O.

[1]

[Total: 15]

3


ForExaminer's

Use

© UCLES 2005



2 FA 3 contains two cations and two anions from those listed on pages 6 and 7.

In all tests, the reagent should be added gradually until no further change is observed, withshaking after each addition.Record your observations in the spaces provided.Your answers should include• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.You should indicate clearly at what stage in a test a change occurs.


4

9701/03/M/J/05

ForExaminer's

Use

© UCLES 2005



(a) To 3 cm depth of FA 3 in a boiling-tube,add 2 cm depth of dilute sulphuric acid.

Warm the mixture and leave to stand forseveral minutes. Continue with test (b).

Care – mixtures containing precipitatescan “bump” when heated and eject thehot acid from the tube.

Use a teat pipette to transfer 1 cm depthof the solution into a test-tube and addan equal depth of distilled water.Add aqueous sodium hydroxide, drop bydrop, until there is no further change.

(b) To 1 cm depth of FA 3 in a boiling-tube,add 2 cm depth of aqueous sodiumhydroxide. Add a piece of aluminium foiland warm the tube.

Care – solutions containing sodiumhydroxide when heated can “bump” andeject the hot alkali from the tube.Remember to complete test (a) if youhave not yet done so.

(c) To 3 cm depth of FA 3 in a boiling-tube,add an equal depth of aqueousammonia.

Filter the solution.

Add aqueous potassium chromate(VI) tothe filtrate.



(d) To 1 cm depth of FA 3 in a boiling-tube,add 1 cm depth of aqueous silver nitrate.

Warm the mixture and carefully pouraway the solution. Wash the precipitatethat remains with distilled water anddiscard the water.

Add aqueous ammonia to the washedprecipitate.

5


ForExaminer's

Use

© UCLES 2005

Test Observations

Use the information in the Qualitative Analysis Tables on pages 6 and 7 to identify the ionspresent in FA 3. For each ion give one piece of evidence that supports your choice.

Cation 1 present in FA 3 …………………………………………………

Evidence for Cation 1

.........................................................................................................................................................

.................................................................................................................................................... [1]

Cation 2 present in FA 3 …………………………………………………

Evidence for Cation 2

.........................................................................................................................................................

.................................................................................................................................................... [1]

Anion 1 present in FA 3 …………………………………………………

Evidence for Anion 1

.........................................................................................................................................................

.................................................................................................................................................... [1]

Anion 2 present in FA 3 …………………………………………………

Evidence for Anion 2

.........................................................................................................................................................

.................................................................................................................................................... [1]

[Total: 10]







6

9701/03/M/J/05© UCLES 2005

aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion



© UCLES 2005


3 Tests for gases

7

9701/03/M/J/05

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2




BLANK PAGE

8

9701/03/M/J/05

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Everyreasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, thepublisher will be pleased to make amends at the earliest possible opportunity.





SP (SJF3983) T12463/2© UCLES 2006 [Turn over



CHEMISTRY 9701/03




Write your details, including practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Tests for gases are provided on page 8.You may use a calculator.At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.



1

2

TOTAL

SESSION

LABORATORY



© UCLES 2006

2

9701/03/M/J/06

ForExaminer's

Use1 FA 1 is an aqueous bleach named ‘Superclean’.

FA 2 is a solution containing 19.78 g dm–3 of sodium thiosulphate, Na2S2O3.

You are also provided with: aqueous potassium iodide, KI,1.0 mol dm–3 sulphuric acid, H2SO4,starch indicator solution,distilled water.

Many commercial bleaches contain compounds of chlorine as the ‘active ingredient’. Theyare able to displace iodine from aqueous potassium iodide. This iodine can be titratedagainst sodium thiosulphate to determine the ‘free chlorine’ concentration for the bleach.You are to determine the ‘free chlorine’ concentration in ‘Superclean’.

(a) Dilution of ‘Superclean’

Pipette 25.0 cm3 of FA 1 into the 250 cm3 graduated flask, labelled FA 3. Make thesolution up to 250 cm3 with distilled water and mix the solution thoroughly.This solution is FA 3.

(b) Titration of iodine produced on reacting FA 3 with an excess of iodide ions

Rinse the 25 cm3 pipette used in (a), firstly with water and then with FA 3. Pipette25.0 cm3 of FA 3 into a conical flask and, using a measuring cylinder, add to the flask10 cm3 of aqueous potassium iodide and 10 cm3 of 1.0 mol dm–3 sulphuric acid.

Fill the burette with FA 2 and titrate the displaced iodine until the colour of the solutionbecomes pale yellow. Then add 1 cm3 of starch indicator solution. Swirl the flask to mixthe indicator and solution, then continue the titration until the blue colour of the starch/iodine complex disappears, leaving a colourless solution. This is the end-point.



Table 1.1 Titration of liberated iodine with FA 2

[7]

Summary

25.0 cm3 of FA 3 displaced iodine that reacted with ………………. cm3 of FA 2.

Show which results you used to obtain this volume of FA 2 by placing a tick (✓) underthe readings in Table 1.1.







(c) Calculate how many moles of sodium thiosulphate, Na2S2O3, were run from theburette during the titration.[Ar: Na, 23.0; S, 32.1; O, 16.0]

[2]

(d) Calculate how many moles of iodine, I2, were present in the conical flask after FA 3reacted with an excess of iodide ions.

2S2O32–(aq) + I2(aq) → S4O6

2–(aq) + 2I–(aq)

[1]

(e) 1 mol of iodine is displaced by 1 mol of ‘free chlorine’.

Cl2(aq) + 2I–(aq) → 2Cl –(aq) + I2(aq)

Calculate the ‘free chlorine’ concentration, in mol dm–3, of FA1, the bleach ‘Superclean’.

[3]

3


ForExaminer's

Use

© UCLES 2006



(f) The ‘free chlorine’ concentration of a second bleach, ‘Germfree’, is found by the samemethod.

50.0 cm3 of ‘Germfree’ is pipetted into a 250 cm3 graduated flask and the solutionmade up to 250 cm3 with distilled water. The ‘free chlorine’ concentration in the dilutedsolution is found to be 0.082 mol dm–3.

Calculate the ‘free chlorine’ concentration, in mol dm–3, in ‘Germfree’.

[1]

(g) The cost of each bleach is as follows.

‘Superclean’ $2.80 dm–3 ‘Germfree’ $1.80 dm–3

Use the data above and your answers to (e) and (f) to show which of the bleaches isbetter value for money.

[1]

[Total: 15]

4

9701/03/M/J/06

ForExaminer's

Use

© UCLES 2006



BLANK PAGE

5




6

9701/03/M/J/06

ForExaminer's

Use

© UCLES 2006© UCLES 2006

2 You are provided with four aqueous solutions, FA 4, FA 5, FA 6 and FA 7.

Each solution contains one of the following.

an alcoholan aldehydea carboxylic acida ketone

You are to perform the tests below and from the results establish which type of organiccompound is contained in each of FA 4, FA 5, FA 6 and FA 7.

After each test discard the contents of the tubes into the 250 cm3 beaker, labelled organicwaste. Rinse and re-use the tubes for the remaining tests.

Tests for gases are printed on page 8.

Record your results in the table on page 7. Where no reaction has taken place,write ‘no change’ in the appropriate box in the table.

test (a)

test (b)

test (c)

test (d)

test (e)

Place 1 cm depth of each of the solutions FA 4, FA 5, FA 6 and FA 7 into separatetest-tubes.

To each tube add a small quantity of magnesium powder or turnings.

Identify any gas given off and record the test you used to make the identification.


To each tube add a small quantity of powdered sodium carbonate.

Identify any gas given off and record the test you used to make the identification.


To each tube add 1 cm depth of 2,4-dinitrophenylhydrazine reagent.


Place 2 cm depth of aqueous silver nitrate in a boiling-tube and add to it 1 cmdepth of aqueous sodium hydroxide. This will produce a precipitate of silver oxide.

Use a dropping pipette to add dilute aqueous ammonia to this mixture until theprecipitate of silver oxide just dissolves.

Do not add an excess of aqueous ammonia.

To each of the tubes containing FA 4, FA 5, FA 6 and FA 7 add 1 cm depth of thesilver-containing solution you have just prepared.

Place 1 cm depth of each of the solutions FA 4, FA 5, FA 6 and FA 7 into separateboiling-tubes.

To each tube add a few drops of acidified potassium dichromate(VI) to give ayellow-orange solution. Warm the tube gently.



7

9701/03/M/J/06

ForExaminer's

Use

© UCLES 2006

[8]

Identify the type of organic compound present in each of the solutions FA 4, FA 5, FA 6 and FA 7 and complete the table below.

[2]

[Total: 10]

test

(a)

(b)

(c)

(d)

(e)

FA 4 FA 5 FA 6 FA 7

FA 4

type of organic compoundcontained in the solution

confirmed by the observations in test(s)

FA 5

FA 6

FA 7



Tests for gases

8

9701/03/M/J/06© UCLES 2006








ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2







SP (SLM) T38775/5© UCLES 2007 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of Education Advanced Subsidiary Level and Advanced Level


Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate in the boxes provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE ON ANY BARCODES.

Answer all questions.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.

Qualitative Analysis Notes are printed on pages 10 and 11.

At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.

*3963816257*

CHEMISTRY 9701/31

Paper 31 Practical Test May/June 2007

2 hours

Candidates answer on the Question Paper.

Additional Materials: As listed in the Instructions to Supervisors


1

2

3

Total

Session

Laboratory



2

9701/31/M/J/07

ForExaminer’s

Use

© UCLES 2007

1 You are required to find the percentage purity of a sample of sodium carbonate, Na2CO3.

FA 1 contains 4.50 g dm–3 of the impure sodium carbonate.FA 2 is 0.50 mol dm–3 hydrochloric acid, HCl.

(a) Dilution of FA 2

By using a burette, measure between 33.00 cm3 and 34.00 cm3 of FA 2 into the 250 cm3 graduated flask labelled FA 3.

Record your burette readings and the volume of FA 2 added to the flask in the space below.

Make up the contents of the flask to the 250 cm3 mark with distilled water. Place the stopper in the flask and mix the contents thoroughly by slowly inverting the flask a number of times.

Titration

Fill a second burette with FA 3, the diluted solution of hydrochloric acid.

Pipette 25.0 cm3 of FA 1 into a conical flask. Add a few drops of methyl orange indicator and titrate with FA 3.

Perform a rough (trial) titration and sufficient further titrations to obtain accurate results.

Record your titration results in the space below. Make certain that your recorded results show the precision of your working.

[6]

(b) From your titration results obtain a suitable volume of FA 3 to be used in your calculations.

Show clearly how you obtained this volume.

[1]

i

ii

iii

iv

v

vi



3


ForExaminer’s

Use

© UCLES 2007

Calculations

Show your working and appropriate significant figures in all of your calculations.

(c) Calculate how many moles of HCl are contained in the FA 2 run into the graduated flask.

............................mol of HCl were run into the graduated flask.

Calculate how many moles of HCl are contained in the volume of FA 3 which reacted with 25.0 cm3 of FA 1.

............................mol of HCl reacted with 25.0 cm3 of FA 1.

Use this answer to calculate how many moles of sodium carbonate, Na2CO3, are present in 1.00 dm3 of FA 1.

Na2CO3 + 2HCl → 2NaCl + CO2 + H2O

............................mol of Na2CO3 are present in 1.00 dm3 of FA 1.

Calculate the mass of sodium carbonate, Na2CO3, in 1.00 dm3 of FA 1. [Ar: C, 12.0; O, 16.0; Na, 23.0]

FA 1 is ............................g dm–3 of Na2CO3.

Calculate, to 3 significant figures, the percentage purity of the sodium carbonate, Na2CO3, dissolved in FA 1.

The percentage purity of the sodium carbonate dissolved in FA 1 is ............................%.

[5]

i

ii

iii

iv

v



4

9701/31/M/J/07

ForExaminer’s

Use

© UCLES 2007

(d) Look at the scale on the 25 cm3 measuring cylinder provided. Record the smallest scale division on the measuring cylinder and estimate the error in reading the scale.

smallest division = ........................ cm3

estimated error = ± ...................... cm3

If 25 cm3 of FA 1 is measured with a measuring cylinder, calculate the estimated percentage error.

The estimated error is ...................................................%.

Your pipette is calibrated with an error of ±0.06 cm3. Calculate the percentage error when measuring 25.0 cm3 of solution with this pipette.

The error is ..................................................%. [2]



5


ForExaminer’s

Use

© UCLES 2007

(e) Use the measuring cylinder to place 25 cm3 of FA 1 into a conical flask. Add methyl orange indicator as before and titrate with FA 3. Repeat the titration once using the measuring cylinder. Record your results below.

Would you expect to be able to obtain consistent titres using a measuring cylinder? Explain your answer.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(f) A student suspects that the presence of dissolved carbon dioxide affects the end-point of the titration.

Suggest a simple modification to the experimental technique to eliminate the dissolved carbon dioxide as the titration is performed.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total: 16]



6

9701/31/M/J/07

ForExaminer’s

Use

© UCLES 2007

2 Read through the question before starting any practical work.

The percentage purity of the sodium carbonate can also be determined by measuring the temperature change when a weighed sample of the solid carbonate reacts with an excess of hydrochloric acid and the following information is used.

Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l) ∆H = –37.0 kJ mol–1

You are provided with the following.FA 4, impure solid sodium carbonateFA 5, 2.0 mol dm–3 hydrochloric acid

Measurement of temperature change

(a) Follow the instructions below to determine the percentage purity of the sodium carbonate.

You will carry out the experiment twice.

• Weigh the empty weighing bottle.• Reweigh the bottle with between 4.00 g and 4.50 g of FA 4.• Support the plastic cup in the 250 cm3 beaker and add to it, from a measuring

cylinder, 50 cm3 of FA 5.• Measure and record the steady temperature of the FA 5 in the plastic cup.• Add the FA 4 from the weighing bottle to the plastic cup, a little at a time to

prevent acid spray. Stir and record the highest temperature reached.• Reweigh the empty weighing bottle.

In an appropriate format in the space below, record• all measurements of mass and temperature,• the mass of FA 4 used, m,• the temperature rise, ∆T.

Empty and rinse the plastic cup. Repeat the experiment.

Results

[4]



7


ForExaminer’s

Use

© UCLES 2007

Calculations

(b) For each experiment calculate ∆Tm

, the temperature rise per gram of FA 4 used.

first experiment ∆Tm

= ................ °C g–1 second experiment ∆Tm

= ................ °C g–1

Calculate the mean value of ∆Tm

.

The mean value of ∆Tm

= ............................................ °C g–1

[2]

(c) Is one repeat of the experiment sufficient or should it be repeated again? Explain your answer.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(d) Calculate the percentage purity of the sodium carbonate using the following expression. Note, this value is likely to be different from the one you obtained in question 1.

purity = ∆Tm

× 137.0

× 2279%

purity = ..............................................% [1]

[Total: 8]



8

9701/31/M/J/07

ForExaminer’s

Use

© UCLES 2007

3 FA 6 and FA 7 are solids each containing one cation and one anion from those listed on page 10 and page 11.

You will dissolve each solid in dilute nitric acid, HNO3, and use the solutions formed in reactions with aqueous sodium hydroxide, NaOH, and aqueous ammonia, NH3.

At each stage you are to record details of the following.• colour changes seen• the formation of any precipitate• the solubility of any precipitate in an excess of the reagent added

Where gases are released they should be identified by a test, described in the appropriate place in your observations.


Marks are not given for chemical equations.

No additional tests for ions present should be attempted.

(a) Preparation of the solutions

Dissolve each solid separately in dilute HNO3 in a 100 cm3 beaker. Use the minimum quantity of acid, added a little at a time and warm to dissolve the solid if necessary. Then add distilled water to each solution to give a total volume of about 60 cm3.

Record your observations in the space below.

[4]

(b) Reactions of the solutions formed in (a) with NaOH(aq) and NH3(aq)

Use separate portions of each of the solutions formed in (a) in reactions with aqueous NaOH and with aqueous NH3, added until in excess.

For each test use 1 cm depth of solution in a boiling-tube. Record details of the tests performed and the observations made.



9

9701/31/M/J/07

ForExaminer’s

Use

© UCLES 2007

[6]

(c) Both cations and one anion can now be definitely identified.

cation in FA 6 ....................................................................................................................

evidence ...........................................................................................................................

cation in FA 7 ....................................................................................................................

evidence ...........................................................................................................................

The anion in FA ................... is ........................................................................................

evidence ........................................................................................................................... [3]

(d) Tests to identify the remaining anion. Do not carry out these tests.

From the Quantitative Analysis Notes for anions select two reagents which could be used, in one test, to indicate the presence of chloride ions in one of the solutions.

Describe how you would use these reagents and the expected observations if the chloride ion were present.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Select another reagent that would also indicate the presence of a chloride ion in the solution. Describe the expected observation if the chloride ion were present.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[3]

[Total: 16]



10

9701/31/M/J/07© UCLES 2007

Qualitative Analysis Notes

Key: [ppt. = precipitate]


ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4

+(aq)ammonia produced on heating

barium,Ba2+(aq)

no ppt. (if reagents are pure) no ppt.

calcium,Ca2+(aq)

white ppt. with high [Ca2+(aq)] no ppt.


grey-green ppt. soluble in excess giving dark green solution


copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






11

9701/31/M/J/07© UCLES 2007


ion reaction

carbonate,CO3

2–CO2 liberated by dilute acids

chromate(VI),CrO4

2–(aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl –(aq)


bromide,Br –(aq)

gives pale cream ppt. with Ag+(aq) (partially soluble in NH3(aq));gives white ppt. with Pb2+(aq)

iodide,I– (aq)


nitrate,NO3

– (aq)NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO2

–(aq)NH3 liberated on heating with OH–(aq) and Al foil;NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulphate,SO4

2– (aq)gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid)

sulphite,SO3

2– (aq)SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases


ammonia, NH3 turns damp red litmus paper blue

carbon dioxide, CO2 gives a white ppt. with limewater(ppt. dissolves with excess CO2)

chlorine, Cl2 bleaches damp litmus paper

hydrogen, H2 ‘pops’ with a lighted splint

oxygen, O2 relights a glowing splint

sulphur dioxide, SO2 turns potassium dichromate(VI) (aq) from orange to green



12

9701/31/M/J/07

BLANK PAGE

Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity.

University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.




Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate in the boxes provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.




*2331107163*


SP (CW) T38779/4© UCLES 2007 [Turn over


CHEMISTRY 9701/32

Paper 32 Practical Test May/June 2007

2 hours



Session

Laboratory


1

2

3

Total



2

9701/32/M/J/07

ForExaminer’s

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© UCLES 2007

1 You are required to determine the concentration in g dm–3 of hydrated ammonium iron(II) sulphate, (NH4)2SO4.FeSO4.6H2O, in the solution FB 1.

FB 1 contains hydrated ammonium iron(II) sulphate. FB 2 is 0.0120 mol dm–3 potassium manganate(VII), KMnO4.

(a) Dilution of FB 1

By using a burette measure between 36.00 cm3 and 37.00 cm3 of FB 1 into the 250 cm3 graduated flask labelled FB 3.

Record your burette readings and the volume of FB 1 added to the flask in the space below.


Titration

Fill a second burette with FB 2.

Pipette 25.0 cm3 of FB 3 into a conical flask. Use a measuring cylinder to add approximately 10 cm3 of 1.0 mol dm–3 sulphuric acid, H2SO4, and titrate with FB 2 until the first permanent pink colour remains in the solution.

Perform one rough (trial) titration and sufficient further titrations to obtain accurate results.


[6]

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(b) From your titration results obtain a suitable volume of FB 2 to be used in your calculations.

Show clearly how you obtained this volume.

[1]

Calculations


(c) Calculate how many moles of KMnO4 were run from the burette during the titration.

........................ mol of KMnO4 were run from the burette.

Calculate how many moles of Fe2+ ions reacted with the KMnO4 run from the burette.

MnO4–(aq) + 5Fe2+(aq) + 8H+(aq) Mn2+(aq) + 5Fe3+(aq) + 4H2O(I)

........................ mol of Fe2+ reacted with the KMnO4 run from the burette.

Calculate the concentration, in mol dm–3, of Fe2+ in FB 3.

Concentration of Fe2+ in FB 3 = ........................ mol dm–3.



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© UCLES 2007

Calculate the concentration, in mol dm–3, of Fe2+ in FB 1.

Concentration of Fe2+ in FB 1 = ........................ mol dm–3.

Calculate, to 4 significant figures, the concentration of (NH4)2SO4.FeSO4.6H2O in FB 1 in g dm–3 .

[Ar: Fe, 55.8; H, 1.0; N, 14.0; O, 16.0; S, 32.1]

FB 1 contains ........................ g dm–3 of (NH4)2SO4.FeSO4.6H2O. [5]

(d) A student learns that the solution of the iron(II) salt has been prepared by dissolving the solid in distilled water that has absorbed air from the laboratory.

Suggest a way in which the distilled water can be prepared and stored in the laboratory to ensure that it contains a minimum of dissolved air.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(e) Estimate the error in reading a volume from a burette.

smallest division on burette scale = ........................ cm3

estimated error in reading a volume = ± ........................ cm3 [1]

(f) A titre value is obtained by the difference between final and initial burette readings.

What is the maximum possible error in obtaining a titre reading?

estimated maximum error in the titre = ± ........................ cm3 [1]

(g) During one titration a student reads the burette twice. Each reading has an error but the titre has no error. Explain how this can happen.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total: 16]

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© UCLES 2007

2 Read through the question before starting any practical work.

You are required to determine the enthalpy change when citric acid reacts with an excess of sodium hydrogencarbonate.

Citric acid, found in citrus fruit such as lemons and limes, is 2-hydroxypropane-1,2,3-tricarboxylic acid.

CH2-CO2H I C(OH)-CO2H I CH2-CO2H

FB 4 is 0.8 mol dm–3 citric acid. FB 5 is solid sodium hydrogencarbonate, NaHCO3.

(a) Citric acid is a triprotic (tribasic) acid – one mole of the acid reacts with three moles of sodium hydrogencarbonate.

Calculate the minimum mass of sodium hydrogencarbonate that will react with all of the acid in 50.0 cm3 of FB 4.

[Ar: Na, 23.0; H, 1.0; C, 12.0; O, 16.0]

mass of NaHCO3 = ........................ g [1]

(b) Method

Follow the instructions below to determine the enthalpy change for the reaction. You will carry out the experiment twice.

• Weigh the empty weighing bottle. • Weigh the bottle with between 11.5 g and 12.0 g, an excess, of FB 5. • Support the plastic cup in the 250 cm3 beaker and pipette into it 50.0 cm3 of FB 4. • Measure and record the steady temperature of the FB 4 in the plastic cup. • Add the FB 5 from the weighing bottle, a little at a time, to the plastic cup. • Stir and record the lowest temperature reached. • Reweigh the empty weighing bottle.

In an appropriate form at the top of the next page record • all measurements of mass and temperature, • the temperature fall, ΔT.

Empty and rinse the plastic cup.

Repeat the experiment and calculate the mean value of ΔT.



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Results

The mean value of ΔT is ........................ °C.

[6]

(c) Calculate the enthalpy change of reaction using the following expression.

ΔHreaction = mean ΔT × 4.3 kJ mol–1

Your answer should include the appropriate sign.

ΔHreaction = ........................ kJ mol–1 [1]

[Total: 8]



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© UCLES 2007

3 You are provided with three solutions, FB 6, FB 7 and FB 8, each containing one cation and one anion.

One or more of the solutions contains a halide ion. One or more of the solutions contains a sulphate or sulphite ion.

Identification of the anions in FB 6, FB 7 and FB 8

(a) By reference to the Qualitative Analysis Notes on page 12 you are to select and use

(i) one reagent to precipitate any halide ion that is present,

(ii) a second reagent to confirm the identity of any halide ion present.

Because the solutions are coloured you will need to remove traces of solution from the precipitates.

Record the tests performed, the practical procedures used and the observations made for each of the solutions.

Present this information as clearly as possible in a suitable format in the space below.

Use your observations to identify any halide ions present in the solutions FB 6, FB 7 and FB 8 and state which ion is present in which solution.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[7]

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(b) Select reagents and carry out tests

(i) to show which of the solutions contains a sulphate ion or a sulphite ion, and

(ii) to establish which of these ions is present.

Record your tests and observations below.

State which of the ions, sulphate or sulphite, is present in which of the solutions FB 6, FB 7 and FB 8 and explain how you reached this conclusion from your tests above.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[3]

Identification of the cations in FB 6, FB 7 and FB 8

(c) Using aqueous sodium hydroxide and aqueous ammonia it is possible to identify two of the cations present and to draw some conclusions about the nature of the remaining cation.

Carry out tests with these reagents, recording details of what you did and observed in a suitable format in the space below.

[4]



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(d) Explain how your observations in (c) identify two of the cations present and which of the solutions contain those cations.

The cation contained in solution FB ................... is ...................

explanation

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

The cation contained in solution FB ................... is ...................

explanation

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

What conclusion of a general nature about the third cation can you draw from your observations in (c)?

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [2]

[Total: 16]



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Key: [ppt. = precipitate.]


reaction with

NaOH(aq) NH3(aq)

aluminium,Al3+(aq)



ammonium,NH4


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/M/J/07© UCLES 2007


ion reaction

carbonate,CO3

2– CO2 liberated by dilute acids

chromate(VI),CrO4

2– (aq)


chloride,Cl– (aq)


bromide,Br– (aq)


iodide,I– (aq)


nitrate,NO3

– (aq) NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO2

– (aq)

NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO (pale) brown NO2 in air)

sulphate,SO4


sulphite,SO3


3 Tests for gases

gas test and test results


carbon dioxide, CO2gives a white ppt. with limewater(ppt. dissolves with excess CO2)

chloride, Cl2 bleaches damp litmus paper

hydrogen, H2 “pops” with a lighted splint








SPA (NF/KN) T58586/1© UCLES 2008 [Turn over



Write your Centre number, candidate number and name on all the work you hand in.Give details of the practical session and laboratory where appropriate, in the boxes provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.




*5947007489*

CHEMISTRY 9701/31

Paper 31 Advanced Practical Skills May/June 2008

2 hours



Session

Laboratory


1

2

Total



2

9701/31/M/J/08© UCLES 2008

ForExaminer’s

Use

1 Read through question 1 before starting any practical work.

You are provided with the following reagents. • FA 1 containing 15.68 g dm–3 of hydrated ammonium iron(II) sulphate (NH4)2SO4.FeSO4.6H2O • FA 2, 0.015 mol dm–3 potassium manganate(VII), KMnO4 • FA 3 containing 0.025 mol dm–3 of a reagent X • 1.0 mol dm–3 sulphuric acid, H2SO4

Iron(II) ions, Fe2+, are oxidised by acidified manganate(VII) ions.

MnO–4 (aq) + 8H+(aq) + 5e– → Mn2+(aq) + 4H2O(l)

Fe2+(aq) → Fe3+(aq) + e–

Reagent X oxidises Fe2+ to Fe3+ and is also oxidised by acidified MnO–4 .

If varying volumes of FA 3, containing reagent X, are added to 25.0 cm3 of FA 1 in the presence of H2SO4 and the mixtures are titrated against FA 2, a graph of the results can be drawn as shown.

titre / cm3


Z0.00

0.00

You are to determine experimentally

• Z, the exact volume of FA 3 which reacts with 25.0 cm3 of FA 1,

• the mole ratio for the reaction of FA 1 with reagent X.

(a) Method

• Fill a burette with FA 2. • Pipette 25.0 cm3 of FA 1 into a conical flask. • Use a measuring cylinder to add approximately 10 cm3 of 1.0 mol dm–3 H2SO4 to

the solution in the flask. • Titrate the FA 1 in the flask with FA 2 until the first permanent pink colour remains

in the solution.

The end-point should be found after the addition of approximately 13 cm3 of FA 2. One titration, performed accurately, will be sufficient.

You are reminded that just before the end-point the pink colour from a single drop of FA 2 spreads through the whole of the solution before disappearing.



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Record your titration results in the space below.

[1]

(b) Method

• Fill the second burette with FA 3. • Empty and rinse the conical flask used in part (a). • Pipette 25.0 cm3 of FA 1 into the conical flask and add 10 cm3 of H2SO4 using a

measuring cylinder. • Run 12.00 cm3 of FA 3 from the second burette into the flask. • Titrate against FA 2 until the first permanent pink colour remains in the solution.

The end-point should be found after the addition of approximately 5 cm3 of FA 2. One titration, performed accurately, will be sufficient.

You are reminded that just before the end-point the pink colour from a single drop of FA 2 spreads through the whole of the solution before disappearing.

Record your titration results in the space below.

[1]

(c) The volume of FA 3 added to the flask in (b) reacts with some but not all of the FA 1 present. Calculate the difference between the titres obtained in parts (a) and (b). Use this difference and the volume of FA 3 added to the flask in (b) to calculate the volume of FA 3 that you would expect to react with all of the Fe2+ ions in 25.0 cm3 of FA 1.

volume of FA 3 = .............................................. cm3

[1]



4

9701/31/M/J/08© UCLES 2008

ForExaminer’s

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(d) The value you have obtained in (c) is an approximate value of Z. You are to perform four more titrations, each with a different volume of FA 3 added to 25.0 cm3 of FA 1, in order to plot a graph of the form shown on page 2 and to obtain an exact value for Z.

One titration, performed accurately, will be sufficient for each volume of FA 3 added.

The volume of FA 3 you have obtained in (c) will help you to choose suitable volumes of FA 3 to be added for each titration.

(If you were unable to calculate the volume of FA 3 in (c) assume that the value lies in the range 19.0 cm3 to 21.0 cm3.)

Remember

• you should not use more than 40.0 cm3 of FA 3 for any single titration, • you already have data for titrations with no FA 3 added and with 12.00 cm3 added.

Prepare a table in the space below and use it to record the titration results for each volume of FA 3 added. Include in your table the titre values from parts (a) and (b).

[6]

(e) Use the grid on the opposite page to plot a graph of titre against volume of FA 3 added.

Draw two straight lines through the plotted points to find Z, the volume of FA 3 that just reacts with the Fe2+ ions in 25.0 cm3 of FA 1.

Z, the volume of FA 3 read from the graph is .............................................. cm3.



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[7]



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(f) Circle on the graph one point where a repeat titration might be appropriate and justify you decision. If you do not think that any titration needs to be repeated, explain why you have come to that conclusion.

..........................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [1]

Calculations

Show your working and appropriate significant figures in all of your calculations. [2]

(g) Calculate how many moles of Fe2+ ions were pipetted into the flask. [Ar: Fe, 55.8; H, 1.0; N, 14.0; O, 16.0; S, 32.1]

............................. mol of Fe2+ were pipetted into the flask. [2]

(h) Calculate how many moles of X are present in Z, the volume of FA 3 read from your graph.

..................... mol of X were present in ................... cm3 of FA 3. [1]

(i) Calculate, to 3 significant figures, the number of moles of Fe2+ ions that react with 1 mol of X.

[2] [Total: 24]



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ForExaminer’s

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2 The three solutions FA 4, FA 5, and FA 6 each contain one of the following. aluminium sulphate, Al2(SO4)3

ammonium iodide, NH4I zinc nitrate, Zn(NO3)2

(a) Use the information on page 12 to select two suitable reagents to use to discover which solution contains iodide ions.

Record, in the space below, the reagents used and the observations made.

From these tests, solution FA ............... contains iodide ions. [5]

You are to perform the tests given in the table opposite on each of FA 4, FA 5 and FA 6 to identify, where possible, the cation and anion present in each solution.

Record details of colour changes seen, the formation of any precipitate and the solubility of any such precipitate in an excess of the reagent added.

Where gases are released they should be identified by a test, described in the appropriate place in your table.


Marks are not given for chemical equations. No additional tests for ions present should be attempted.



9


ForExaminer’s

Usetest observations with

FA 4observations with

FA 5observations with

FA 6

(b) To 1 cm depth of solution in a test-tube, add aqueous sodium hydroxide drop-by-drop until it is in excess.

(c) To 1 cm depth of solution in a test-tube, add aqueous ammonia drop-by-drop until it is in excess.

(d) To 1 cm depth of solution in a test-tube, add aqueous barium chloride,

then

add dilute hydrochloric acid.

(e) To 1 cm depth of solution in a boiling-tube add 2 cm depth of water and 1 cm depth of aqueous lead(II) nitrate,

then

if a precipitate has formed, cautiously warm until the solution boils,

then

cool the tube by standing it in a beaker

of cold water.

[6]



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(f) For each of the solutions FA 4, FA 5, and FA 6, summarise the evidence from the tests performed to identify the cations and anions present.

State clearly where a cation or an anion has not been specifically identified.

FA 4 contains ...................................................................................................................

supporting evidence

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

FA 5 contains ...................................................................................................................

supporting evidence

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

FA 6 contains ...................................................................................................................

supporting evidence

..........................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [4]

(g) When testing a solution containing both NH4I and Zn(NO3)2, suggest why a student should identify the NH

+4 ion before attempting to identify the NO

–3 ion. The Qualitative

Analysis Notes on pages 11 and 12 should help you to answer this.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

...................................................................................................................................... [1]

[Total: 16]



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9701/31/M/J/08© UCLES 2008




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/31/M/J/08© UCLES 2008


ion reaction

carbonate,CO2–

3


chromate(VI),CrO2–

4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–

3 (aq)NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO–

2 (aq)NH3 liberated on heating with OH–(aq) and Al foil;NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulphate,SO2–

4 (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids)

sulphite,SO2–

3 (aq)

SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases












This document consists of 12 printed pages.

SP (SM/CGW) T58776/3© UCLES 2008 [Turn over






At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question orpart question.

CHEMISTRY 9701/32


2 hours




1

2

Total

Session

Laboratory

*2330102833*



2

© UCLES 2008

ForExaminer’s

Use

9701/32/M/J/08

1 You are provided with the following.

FB 1, 3.00 mol dm–3 hydrochloric acid, HCl Three tubes containing different mixtures of sodium carbonate, Na2CO3, and sodium

hydrogencarbonate, NaHCO3, each with a total mass of 5.00 g of mixture.

tube labelled mass of Na2CO3 / g mass of NaHCO3 / g % by mass of Na2CO3

FB 2 1.00 4.00 20.0

FB 3 2.50 2.50 50.0

FB 4 4.00 1.00 80.0

You are to determine the temperature change, ∆T, when the contents of each of the tubes FB 2, FB 3 and FB 4 react with an excess of hydrochloric acid, FB 1.

(a) (i) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g of sodium carbonate, Na2CO3. Show your working.

Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)

[Mr: Na2CO3, 106.0]

(ii) Calculate the volume of 3.00 mol dm–3 hydrochloric acid required to react with 5.00 g of sodium hydrogencarbonate, NaHCO3. Show your working.

NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

[Mr: NaHCO3, 84.0]

[2]



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© UCLES 2008 [Turn over

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9701/32/M/J/08

35.00 cm3 of 3.00 mol dm–3 HCl will be used in each experiment – an excess of hydrochloric acid.

(b) Read the following instructions before starting this section.

• Fill a burette with FB 1, 3.00 mol dm–3 HCl.

• Support the plastic cup in a 250 cm3 beaker.

• Run 35.00 cm3 of acid from the burette into the cup.

• Measure the steady temperature of the acid in the plastic cup.

• Tip the contents of the tube labelled FB 2 into the acid as quickly as possible but take care to avoid overflow or acid spray. Stir with the thermometer, measure and record the highest or lowest temperature reached in the reaction.

• Make certain that all of the solid has been transferred from the tube to the cup.Tap the tube if necessary to dislodge any residual solid.

• Empty and rinse the plastic cup with water. Shake out any residual drops of water.

• Repeat the experiment for each of the tubes FB 3 and FB 4.

Record all measurements of temperature and the temperature changes, ∆T, in an appropriate form in the space below. Indicate clearly whether the temperature has increased or decreased in the reaction.

[4]

(c) Select masses of Na2CO3 and NaHCO3 which can be used to prepare two further tubes, each containing a mixture which can be used in the same experiment as described above. The temperature change when each of these mixtures reacts with hydrochloric acid will be used with those above to plot five points on a graph.

tube labelled mass of Na2CO3 / g mass of NaHCO3 / g

FB 5

FB 6

[1]



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© UCLES 2008

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9701/32/M/J/08

(d) Preparation of the tubes FB 5 and FB 6

You are provided with

• empty tubes labelled FB 5 and FB 6,

• sodium carbonate and sodium hydrogencarbonate.

Prepare each tube and record in an appropriate form in the space below

• all of your weighings,

• the mass of sodium carbonate in the mixture,

• the mass of sodium hydrogencarbonate in the mixture,

• the % by mass of sodium carbonate in the mixture.

[4]

(e) Carry out the same experiment as in (b) for each of the tubes FB 5 and FB 6.

Record all temperature readings and the temperature change, ∆T, for each of the tubes.

[2]



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(f) Plot ∆T (y-axis, starting at –10 °C) against the % by mass of Na2CO3 in the mixture(x-axis, starting at 0%).

Remember – the temperature has increased in some experiments and decreased in others.

Draw the most appropriate straight line through the five plotted points. Extend this line until it crosses the y-axis.

[4]

(g) Record from the graph the temperature change when the mixture contains no sodium carbonate. This represents the temperature change for 5.00 g of sodium hydrogencarbonate.

∆T, read from the graph for 0% sodium carbonate is .......................................... °C. [1]



6

© UCLES 2008

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9701/32/M/J/08

(h) You are to use the value in (g), obtained from the graph, to calculate the enthalpy change for the reaction between sodium hydrogencarbonate and hydrochloric acid.

NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

(i) Calculate the energy change in the plastic cup when 5.00 g of NaHCO3 reacts with excess hydrochloric acid.

[4.3 J are absorbed or released when the temperature of 1.0 cm3 of solution changes by 1 °C.]

(ii) Calculate the enthalpy change, ∆H, for the reaction

NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g).

Give your answer in kJ mol–1, correct to 3 significant figures. Include the appropriate sign.

[Mr: NaHCO3, 84.0]

∆H = …...…………………….. kJ mol–1

[4]



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(i) Suggest the most significant source of error in this experiment.

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

(j) Suggest a modification to the experimental procedure that would reduce the error described in (i).

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

(k) Do you think the method used is capable of producing an accurate value for the enthalpy change for the reaction of sodium hydrogencarbonate and hydrochloric acid?

Justify your answer by referring to the results of your experiment.

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

[Total: 25]



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© UCLES 2008

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9701/32/M/J/08

2 The three solutions FB 7, FB 8, and FB 9 each contain one of the following. a cation and the chloride ion manganese(II) sulphate, MnSO4 magnesium sulphate, MgSO4

(a) Using the information on page 12 select two suitable reagents and use them to carry out a test to determine which solutions contain the sulphate ion.

In the space below, record details of the test performed and the observations made.

From this test, solutions FB .......... and FB .......... contain the sulphate ion. [2]

(b) By selecting a further two reagents, carry out a test to confirm the presence of the chlorideion in the remaining solution.

In the space below, record details of the test performed and the observations made.

[2]

You are to perform the tests given in the table opposite on each of FB 7, FB 8 and FB 9 to identify and confirm the cation present in the solution.


Where gases are released they should be identified by a test, described in an appropriate place in the table.






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9701/32/M/J/08

testobservations with

FB 7observations with

FB 8observations with

FB 9

(c) To 1 cm depth of solution in a test-tube, add aqueous sodium hydroxide drop-bydrop until it is in excess.

(d) To 1 cm depth of solution in a test-tube, add aqueous ammonia drop-bydrop until it is in excess.

[4]

(e) Observations made with aqueous sodium hydroxide should have indicated that one of the solutions contains either of two cations. Identify this solution and the two possible cations.

Solution ............................ could contain ............................ or ............................

Make use of the Qualitative Analysis Notes on page 11 to suggest what further test you could do to identify which of the two ions was present.

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

Carry out your suggestion using a boiling-tube. Record the results below and explain how this enables you to identify the ion present.

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................[3]



10

© UCLES 2008

ForExaminer’s

Use

9701/32/M/J/08

(f) For each of the solutions FB 7, FB 8, and FB 9, identify the cation present and give supporting evidence from the observations made.

FB 7 contains ..............................................

supporting evidence

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

FB 8 contains ..............................................

supporting evidence

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

FB 9 contains ..............................................

supporting evidence

.........................................................................................................................................

.........................................................................................................................................

.........................................................................................................................................

[3]

(g) Carry out the tests below on FB 7.

test observations

To 1 cm depth of solution in a boiling-tube, add 2 cm depth of aqueous ammonia, then slowly add 2 cm depth of aqueous hydrogen peroxide.

To 1 cm depth of solution in a boiling-tube, add 2 cm depth of aqueous hydrogen peroxide, then slowly add 2 cm depth of aqueous ammonia.

[1]

[Total: 15]



11

9701/32/M/J/08© UCLES 2008




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/M/J/08© UCLES 2008


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)


sulphite,SO2–

3 (aq)


3 Tests for gases










This document consists of 11 printed pages, 1 blank page and 1 Insert.

SP (SHW 00157 2/08) T67840/3© UCLES 2009 [Turn over







*3156861652*

CHEMISTRY 9701/31


2 hours


Additional Materials: As listed in the Confidential Instructions


1

2

3

Total

Session

Laboratory



2

9701/31/M/J/09© UCLES 2009

ForExaminer’s

Use

1 You are provided with the following. FA 1 is 0.15 mol dm–3 sodium thiosulfate, Na2S2O3. FA 2 is aqueous copper(II) sulfate. You are also provided with a 10% solution of potassium iodide, KI, and starch indicator.

You are required to determine the concentration, in g dm–3, of hydrated copper(II) sulfate, CuSO4.5H2O, in FA 2.

Dilution of FA 2

(a) By using a burette measure between 47.00 cm3 and 47.50 cm3 of FA 2 into the 250 cm3 graduated flask labelled FA 3.



Titration

Fill a second burette with FA 1.

Perform a rough (trial) titration as follows.

Pipette 25.0 cm3 of FA 3 into a conical flask. Use the measuring cylinder provided to add 10 cm3 of 10% potassium iodide to the

flask. The Cu2+ ions in FA 3 oxidise the iodide ions to iodine, I2, which can be titrated with

FA 1. The flask will also contain an off-white precipitate of copper(I) iodide, CuI.

Run FA 1 from the burette, 1 cm3 at a time, until the brown colour of the iodine solution has changed to pale brown.

Add approximately 10 drops of starch indicator. A blue-black colour should be seen as the starch reacts with the residual iodine.

Continue to add FA 1 1 cm3 at a time until the blue-black colour of the starch-iodine complex disappears and there is no further colour change.

In this rough titration .............. cm3 of FA 1 were added.



3


ForExaminer’s

Use

Perform sufficient further titrations to obtain reliable results.


[6]

(b) From your titration results obtain a volume of FA 1 to be used in your calculations. Show clearly how you obtained this volume.

[1]

Calculations Show your working and appropriate significant figures in the final answer to each step of

your calculations.

(c) Use your answer to (b) to calculate how many moles of Na2S2O3 were run from the burette into the conical flask.

………………… mol of Na2S2O3 were run from the burette into the conical flask.

Calculate how many moles of I2 reacted with the Na2S2O3 run from the burette.

2S2O2–3 S4O2–

6 + 2e–

I2 + 2e– 2I–

………………… mol of I2 reacted with the Na2S2O3 run from the burette.

Calculate how many moles of Cu2+ ions reacted with iodide ions to produce this amount of I2.

2Cu2+ + 4I– 2CuI + I2

………………… mol of Cu2+ reacted to form the I2.

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9701/31/M/J/09© UCLES 2009

ForExaminer’s

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Calculate the concentration, in mol dm–3, of Cu2+ in FA 3.

The concentration of Cu2+ in FA 3 is ………………… mol dm–3.

Calculate the concentration, in mol dm–3, of Cu2+ in FA 2.

The concentration of Cu2+ in FA 2 is ………………… mol dm–3.

Calculate the concentration, in g dm–3, of CuSO4.5H2O in FA 2. [Ar: Cu, 63.5; H, 1.0; O, 16.0; S, 32.1]

FA 2 contains ………………… g dm–3 CuSO4.5H2O.[5]

(d) The maximum error in any burette reading is ±0.05 cm3.

Explain how the maximum error in a titration is therefore ±0.10 cm3.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [1]

(e) Calculate the maximum percentage error in the average titre given in (b).

The error is ........................................... %. [1]

[Total: 14]

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BLANK PAGE



6

9701/31/M/J/09© UCLES 2009

ForExaminer’s

Use

2 You are to investigate how the rate of formation of sulfur varies with the concentration of sodium thiosulfate, Na2S2O3, in the reaction below.

Na2S2O3(aq) + 2HCl(aq) S(s) + 2NaCl(aq) + SO2(g) + H2O(l)

Care should be taken to avoid inhalation of SO2(g) that is given off during this reaction.

You are provided with the following. FA 1, 0.15 mol dm–3 Na2S2O3 a measuring cylinder to measure 50 cm3

FA 4, 2.0 mol dm–3 HCl a measuring cylinder or marked tube to measure 5 cm3

a printed insert a stop clock or clock with seconds hand

(a) Method – Read through the instructions before starting any practical work.

• Using the larger measuring cylinder transfer 50 cm3 of FA 1 into a 250 cm3 beaker. • Measure 5 cm3 of FA 4 in the smaller measuring cylinder (or marked tube). • Tip the FA 4 into the FA 1 in the beaker and immediately start timing. • Swirl the beaker to mix the solution and place it on top of the printed insert. • View the printed insert from above so that it is seen through the solution. • Note the time when the printing on the insert just disappears.

• Empty and rinse the beaker. Shake out as much of the rinse water as possible and dry the outside of the beaker.

• Repeat the experiment using 25 cm3 of FA 1 and 25 cm3 of distilled water. Add 5 cm3 of FA 4 to start the reaction.

• Select suitable volumes of FA 1 and distilled water for one further experiment to investigate the effect of sodium thiosulfate concentration on the rate of reaction. Remember to use 5 cm3 of FA 4 and to keep the total volume of FA 1 and distilled water constant.

In an appropriate form record the following below: • all measurements of volume and time (to the nearest second) for each experiment, • calculated values of 1/time which are a measure of the rate of reaction.

Results

[9]

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ForExaminer’s

Use

(b) The total volume in each experiment is constant. Using volumes from the first two experiments, show by simple calculation that the volume of FA 1 used is a measure of its concentration in the reaction mixture.

[1]

(c) What is the relationship between the rate of reaction and the time taken?

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [1]

(d) For each experiment calculate the numerical value of (volume of FA 1 × time).

experiment (volume of FA 1 × time) / (cm3 s)

1

2

3

Use your results in (a) and these calculated values to deduce the relationship between the concentration of Na2S2O3 and the rate of formation of sulfur.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [2]

(e) Outline briefly how you would modify the experimental method to investigate the effect of temperature change on the reaction rate.

..........................................................................................................................................

..........................................................................................................................................

.................................................................................................................................... [1]

[Total: 14]



8

9701/31/M/J/09© UCLES 2009

ForExaminer’s

Use

3 FA 5, FA 6, FA 7 and FA 8 are aqueous solutions each containing one cation and one anion.

You will carry out specified tests to deduce

• the cations present in two of the four solutions, • the anions present in three of the four solutions.

At each stage of any test you are to record details of the following.

• colour changes seen • the formation of any precipitate • the solubility of such precipitates in an excess of the reagent added


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling-tube MUST be used.

(a) Carry out the following tests. Record your observations in the spaces provided in the table.

FA 5 FA 6 FA 7 FA 8

To 1 cm depth of solution in a test-tube add aqueous sodium hydroxide, a little at a time, until in excess.

To 1 cm depth of solution in a test-tube add aqueous ammonia, a little at a time, until in excess.

Using the qualitative analysis notes printed on page 11 and the observations above it is possible to identify the cation present in one of the solutions and also to identify possible cations in another of the solutions.

Solution ....................... contains the single cation ....................................................... .

Solution ....................... contains one of the following cations, ..................................... .[4]

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ForExaminer’s

Use

Rinse and re-use test-tubes.

(b) You are to select suitable reagents and carry out tests on the solutions to identify which solution or solutions contain either a nitrate or a nitrite ion.

Record in an appropriate form below the tests performed and the observations made.

Nitrate or nitrite ions are contained in solution(s) .............................................. . [2]

(c) Carry out the following tests.

FA 5 FA 6 FA 7 FA 8

To 1 cm depth of solution in a test-tube add 1 cm depth of dilute hydrochloric acid.

Use these observations to identify the cation or anion present in each solution and complete the table below.

solution anion/cation present reason for selecting the ion

[4]

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9701/31/M/J/09© UCLES 2009

ForExaminer’s

Use

(d) FA 5 and FA 7 can be mixed to confirm the identity of one ion in each of the two solutions.

test observation

To 1 cm depth of FA 5 in a test-tube add 1 cm depth of FA 7.

This observation confirms the presence of …………… in FA 5 and …………… in FA 7.[2]

[Total: 12]

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11

9701/31/M/J/09© UCLES 2009




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH+

4 (aq)no ppt.ammonia produced on heating

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)

green ppt. turning brown on contact with airinsoluble in excess


iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)




off-white ppt. rapidly turning brown on contact with airinsoluble in excess


zinc,Zn2+(aq)






12

9701/31/M/J/09© UCLES 2009


ion reaction

carbonate,CO2–

3



4 (aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl – (aq)


bromide,Br– (aq)


iodide,I– (aq)


nitrate,NO–

3(aq)NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO–

2(aq)NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO (pale) brown NO2 in air)

sulfate,SO2–

4 (aq)gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid)gives white ppt. with Pb2+(aq)

sulfite,SO2–

3 (aq)SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases




chlorine, Cl 2 bleaches damp litmus paper



sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) (aq) from orange to green






SP (SHW 00157 2/08) T67843/4© UCLES 2009 [Turn over







*2645126014*

CHEMISTRY 9701/32


2 hours




1

2

3

Total

Session

Laboratory



2

9701/32/M/J/09© UCLES 2009

ForExaminer’s

Use

1 You are provided with the following. FB 1 is 0.023 mol dm–3 potassium manganate(VII), KMnO4. FB 2 is aqueous ethanedioic acid, H2C2O4, made by dissolving the hydrated salt,

H2C2O4.2H2O. You are also provided with the following. 1.0 mol dm–3 sulfuric acid, H2SO4 distilled water

You are required to determine the concentration, in g dm–3, of hydrated ethanedioic acid, H2C2O4.2H2O, in FB 2.

Dilution of FB 2

(a) By using a burette, measure between 42.50 cm3 and 43.00 cm3 of FB 2 into the 250 cm3 graduated flask, labelled FB 3.



Titration

Fill a second burette with FB 1.

Pipette 25.0 cm3 of FB 3 into a conical flask. Use the measuring cylinder provided to add to the flask 25 cm3 of 1.0 mol dm–3 sulfuric acid and 40 cm3 of distilled water.

Put the thermometer in the flask and heat the solution until the temperature is just over 65 °C.

Carefully remove the thermometer and place the hot flask under the burette. If the neck of the flask is too hot to hold safely, use a folded paper towel to hold the flask.

Run in 1 cm3 of FB 1. Swirl the flask until the colour of the potassium manganate(VII) has disappeared then continue the titration as normal until a permanent pale pink colour is obtained. This is the end-point.

If a brown colour appears during the titration, reheat the flask to 65 °C. The brown colour should disappear and the titration can be completed as above.

If the brown colour does not disappear on reheating, discard the solution and start the titration again.

Perform a rough (trial) titration and sufficient further titrations to obtain reliable results.


[6]

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ForExaminer’s

Use

(b) From your titration results obtain a volume of FB 1 to be used in your calculations. Show clearly how you obtained this volume.

[1]

Calculations Show your working and appropriate significant figures in the final answer to each step of

your calculations.

(c) Calculate how many moles of KMnO4 were run from the burette into the conical flask.

………………… mol of KMnO4 were run from the burette into the conical flask.

Put the correct number of electrons into each of the following half-equations to balance the electrical charges.

MnO4– + 8H+ + ……… e– Mn2+ + 4H2O

C2O2–4 2CO2 + ……… e–

Calculate how many moles of ethanedioate ions, C2O2–4 , reacted with the KMnO4 run

from the burette.

………………… mol of ethanedioate ions reacted with the KMnO4 run from the burette.

Calculate the concentration, in mol dm–3, of C2O2–4 in FB 3.

The concentration of C2O2–4 in FB 3 is ………………… mol dm–3.

Calculate the concentration, in mol dm–3, of C2O2–4 in FB 2.

The concentration of C2O2–4 in FB 2 is ………………… mol dm–3.

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9701/32/M/J/09© UCLES 2009

ForExaminer’s

Use

Calculate the concentration, in g dm–3, of H2C2O4.2H2O in FB 2. [Ar: H, 1.0; C, 12.0; O, 16.0]

FB 2 contains ………………… g dm–3 H2C2O4.2H2O.

[5]

[Total: 12]

2 You are provided with the following. FB 4, anhydrous sodium carbonate, Na2CO3 FB 5, solid sodium hydrogencarbonate, NaHCO3 3.0 mol dm–3 hydrochloric acid

You are to determine the enthalpy change of reaction, �H, for the following reactions.

Na2CO3(s) + 2HCl (aq) 2NaCl (aq) + CO2(g) + H2O(l) �H1

NaHCO3(s) + HCl (aq) NaCl (aq) + CO2(g) + H2O(l) �H2

(a) Reaction of FB 4, Na2CO3, with an excess of 3.0 mol dm–3 hydrochloric acid

Read through the following instructions carefully before starting the experimental work.

• Support the plastic cup in the 250 cm3 beaker provided. • Use the measuring cylinder to transfer 50 cm3 of 3.0 mol dm–3 hydrochloric acid

into the plastic cup. • Weigh the tube containing FB 4, anhydrous sodium carbonate. • Measure and record the steady temperature of the acid in the beaker. • Add the contents of the tube to the acid in three separate lots, taking care that

the mixture does not overflow. • Stir and record the highest temperature obtained. • Reweigh the tube containing residual FB 4.

Record in an appropriate form below all of your weighings and temperature measurements together with the mass, m1, of FB 4 added and the temperature rise, �T1.

[1]



5


ForExaminer’s

Use

(b) Calculate the temperature rise per gram of FB 4, Na2CO3, used in the experiment.

�T1m1

= ...................................... °C g–1 [2]

(c) Calculate the enthalpy change, �H1, for the following reaction.

Na2CO3(s) + 2HCl (aq) 2NaCl (aq) + CO2(g) + H2O(l)

�H1 = – (22.79 × �T1m1

) kJ mol–1

�H1 = – ........................................ kJ mol–1

(d) Reaction of FB 5, NaHCO3, with an excess of 3.0 mol dm–3 hydrochloric acid

50 cm3 of 3.0 mol dm–3 hydrochloric acid contains 0.15 mol HCl.

Calculate the mass of NaHCO3 that will react with 0.15 mol HCl. [Ar: C, 12.0; H, 1.0; O, 16.0; Na, 23.0]

[1]

The reaction of NaHCO3(s) and HCl (aq) is endothermic.The expected fall in temperature when 1.0 g NaHCO3(s) is added to 50 cm3, an excess, of 3.0 mol dm–3 HCl is approximately 1.5 °C.

(e) The error in reading a –10 °C to +110 °C thermometer is ±0.5 °C.

What is the maximum error when using two temperature measurements to calculate a temperature change?

The maximum error is ± .......................................... °C. [1]

(f) Determine the maximum percentage error in the calculated temperature change when 1.0 g of NaHCO3 is added to 50 cm3 of 3.0 mol dm–3 hydrochloric acid.

The maximum error is ± ........................................... %. [1]



6

9701/32/M/J/09© UCLES 2009

ForExaminer’s

Use

(g) Use your answer to (d) and the expected temperature change of −1.5 °C g–1 to select a mass of FB 5, NaHCO3, to use in an experiment with 50 cm3 of 3.0 mol dm–3 hydrochloric acid. The mass selected should give an appropriate, measurable, temperature fall.

Note: The hydrochloric acid should be in excess and the percentage error in temperature measurement should be kept to a minimum.

Mass of FB 5 to be used = .................................................. g.

Predicted temperature fall = ................................................ °C.[1]

(h) Read through the instructions before starting any practical work.

• Empty, rinse, and shake dry the plastic cup used in (a). • Support the plastic cup in the 250 cm3 beaker provided. • Use the measuring cylinder to transfer 50 cm3 of 3.0 mol dm–3 hydrochloric acid

into the plastic cup. • Weigh the empty tube labelled NaHCO3. • Add the mass of FB 5 you have selected in (g) to the tube and reweigh. • Measure and record the steady temperature of the acid in the beaker. • Add the contents of the tube to the acid in three separate lots, taking care that

the mixture does not overflow. • Stir and record the lowest temperature obtained. • Reweigh the tube containing residual FB 5.

Record in an appropriate form below all of your weighings and temperature measurements together with the mass, m2, of FB 5 added and the temperature fall, �T2.

[2]

(i) Calculate the temperature fall per gram of FB 5, NaHCO3, used in the experiment.

�T2m2

= ........................................... °C g–1

[3]



7


ForExaminer’s

Use

(j) Calculate the enthalpy change, �H2, for the following reaction.

NaHCO3(s) + HCl (aq) NaCl (aq) + CO2(g) + H2O(l)

�H2 = + (18.06 × �T2m2

) kJ mol–1

�H2 = + ........................................ kJ mol–1

(k) It is not possible to measure experimentally the enthalpy change, �H3, for the following reaction as it does not take place in the laboratory.

Na2CO3(s) + CO2(g) + H2O(l) 2NaHCO3(s)

It is possible, however, to calculate a “theoretical” value of �H3 for this reaction from the results of the experiments you have carried out and a Hess cycle.

2HCl (aq) + Na2CO3(s) + H2O(l) + CO2(g) �H3 2NaHCO3(s) + 2HCl (aq)

�H1 2�H2

2NaCl (aq) + 2CO2(g) + 2H2O(l)

Derive an equation to link �H1, �H2, and �H3.

Use your equation and the results from (c) and (j) to calculate a value for �H3.

�H3 = ........................................ kJ mol–1

[2]

(l) Suggest a modification to the experimental method in order to reduce the transfer of heat energy to or from the contents of the plastic cup during the experiment.

..........................................................................................................................................

.................................................................................................................................... [1]

[Total: 15]



8

9701/32/M/J/09© UCLES 2009

ForExaminer’s

Use

3 FB 6 and FB 7 each contain one of the following sodium halides, NaCl, NaBr, NaI.

(a) Place half of the solid FB 6 provided in a test-tube. Half fill the test-tube with distilled water and shake to dissolve the solid. Label the tube FB 6.

Do the same with FB 7, labelling the tube FB 7. Keep the remaining solid for (c).

(b) You are to select appropriate reagents from those provided and to perform tests to identify which halide ion is present in FB 6 and which in FB 7.

Retain some of the FB 7 solution for test (d).

In an appropriate form below record the tests performed and the results of those tests.

From the recorded observations the following halides are identified.

FB 6 contains ......................................................

FB 7 contains ......................................................[4]

(c) Carry out the following tests. [Care: unpleasant fumes may be produced]

test observations

FB 6 FB 7

Place the remaining solid in a clean, dry test-tube and add 5 drops of concentrated sulfuric acid (care: the concentrated acid is very corrosive),

then as soon as you have made your observation,

half fill the test-tube with distilled water to dissolve the remaining solid and any fumes produced.

Transfer 1 cm depth of the resulting solution to a test-tube and add a few drops of starch solution.

[2]

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ForExaminer’s

Use

(d) Carry out the following tests.

test observations

Place 1 cm depth of the solution of FB 7 prepared in (a) in a test-tube.

Add 1 cm depth of aqueous bromine,[Care: unpleasant fumes]then,

add a few drops of starch solution.

[1]

(e) Use your observations and knowledge of halogen chemistry to explain the reactions in (c) and identify the chemical behaviour of the concentrated sulfuric acid in the reaction.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Use your observations and knowledge of halogen chemistry to explain what happens when the solutions are mixed in (d).

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[3]



10

9701/32/M/J/09© UCLES 2009

ForExaminer’s

Use

(f) FB 8 and FB 9 each contain one cation from those listed on page 11.

Carry out the following tests to identify the cation present in each solution.

test observations

FB 8 FB 9

To 1 cm depth of solution in a test-tube, add aqueous sodium hydroxide a little at a time

then,

add an excess of the reagent to give no more than 4 cm depth of solution in the test-tube.

To 1 cm depth of solution in a test-tube, add aqueous ammonia a little at a time

then,

add an excess of the reagent to give no more than 4 cm depth of solution in the test-tube.

The cation present in FB 8 is ......................................................

The cation present in FB 9 is ......................................................[3]

[Total: 13]



11

9701/32/M/J/09© UCLES 2009




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH+

4 (aq)no ppt.ammonia produced on heating

barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/M/J/09© UCLES 2009


ion reaction

carbonate,CO2–

3



4 (aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl – (aq)


bromide,Br– (aq)


iodide,I– (aq)


nitrate,NO–

3(aq)NH3 liberated on heating with OH–(aq) and Al foil

nitrite,NO–

2(aq)NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO (pale) brown NO2 in air)

sulfate,SO2–

4 (aq)gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid)gives white ppt. with Pb2+(aq)

sulfite,SO2–

3 (aq)SO2 liberated with dilute acids;gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases




chlorine, Cl 2 bleaches damp litmus paper



sulfur dioxide, SO2 turns aqueous acidified potassium dichromate(VI) (aq) from orange to green






DC (SJF5445/CGW) 11612/5© UCLES 2010 [Turn over




Answer all questions.You may lose marks if you do not show your working or if you do not use appropriate units.Use of a Data Booklet is unnecessary.



*2141916687*

CHEMISTRY 9701/31


2 hours




1

2

Total

Session

Laboratory

www.XtremePapers.net


2

9701/31/M/J/10© UCLES 2010

ForExaminer’s

Use


You are provided with the following reagents. FA 1, 2 .0 mol dm–3 sulfuric acid, H2SO4 FA 2, aqueous sodium hydroxide, NaOH

The reaction of sulfuric acid with sodium hydroxide is exothermic. In separate experiments you will add increasing volumes of FA 2 to a fixed volume of

FA 1. In each experiment you will measure the maximum temperature rise. As the volume of FA 2 is increased, this maximum temperature rise will increase and then decrease.

By measuring the maximum temperature rise for different mixtures of the two reagents you are to determine the following.

• the concentration of sodium hydroxide, NaOH, in FA 2 • the enthalpy change when 1 mol of H2SO4 is neutralised by NaOH

(a) Method

• Fill the burette with FA 1. • Support the plastic cup in the 250 cm3 beaker. • Run 10.00 cm3 of FA 1 from the burette into the plastic cup. • Measure 10 cm3 of FA 2 in a measuring cylinder. • Place the thermometer in the FA 2 in the measuring cylinder and record the steady

temperature of the solution. • Tip the FA 2 in the measuring cylinder into the plastic cup, stir and record the

maximum temperature obtained in the reaction. • Empty and rinse the plastic cup. Rinse the thermometer. Shake dry the plastic cup. • Carry out the experiment four more times. Each time use 10.00 cm3 of FA 1. Use 20 cm3, 30 cm3, 40 cm3 and 50 cm3 of FA 2 in these different experiments.

Carry out two further experiments. Choose volumes of FA 2 which will allow you to investigate more precisely the volume

of FA 2 that produces the highest temperature rise when added to 10.00 cm3 of FA 1.

Results Record your results in an appropriate form showing, for each experiment, the volumes of solution used, temperature measurements and the temperature rise.

[9]

i

ii

iii

iv

v

vi

vii

viii

ix



3


ForExaminer’s

Use

(b) Use the grid below to plot a graph of temperature rise (y-axis) against the volume of FA 2 added (x-axis).

Draw a line of best fit through the points where the temperature rise is increasing and another line through the points where the temperature rise is decreasing.

The intersection of these lines represents the temperature rise for the volume of FA 2 that exactly neutralises the sulfuric acid present in 10.00 cm3 of FA 1.

[4]

i

ii

iii

iv



4

9701/31/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Read from the graph the volume of FA 2 that gives the maximum temperature rise.

The volume of FA 2 giving the maximum temperature rise is ………….. cm3. [1]

(d) Explain why the temperature rise is plotted on the y-axis rather than on the x-axis.

..........................................................................................................................................

...................................................................................................................................... [1]

(e) Construct the balanced equation for the reaction of sulfuric acid with sodium hydroxide.

...................................................................................................................................... [1]

(f) (i) Calculate how many moles of sulfuric acid, H2SO4, are contained in 10.00 cm3 of FA 1.

10.00 cm3 of FA 1 contain ………….. mol of H2SO4.

(ii) Calculate how many moles of NaOH are required to neutralise the amount of H2SO4 calculated in (i) above.

The sulfuric acid in 10.00 cm3 of FA 1 is neutralised by ………… mol of NaOH. [2]

(g) Use the equation below to calculate the concentration of NaOH in FA 2.

concentration of NaOH (mol dm–3) = answer to (f)(ii) × 1000volume of FA 2 (cm3) from (c)

The concentration of NaOH in FA 2 = ………………………. mol dm–3. [1]

(h) Read the maximum temperature rise from the graph and use this to calculate the enthalpy change when 1 mol H2SO4 is neutralised by NaOH. Give your answer in kJ mol–1 and include the correct sign for the reaction.

[4.3 J are absorbed or released when the temperature of 1 cm3 of solution changes by 1 °C. Remember that separate volumes of FA 1 and FA 2 were mixed together.]

ΔH = ……………………… kJ mol–1. [2]



5


ForExaminer’s

Use

(i) A student suggested that the accuracy of the experiment would be improved if the volume of FA 2 had been measured using a burette rather than a measuring cylinder.

Suggest an advantage and a disadvantage of using a burette in the procedure.

advantage ........................................................................................................................

..........................................................................................................................................

disadvantage ...................................................................................................................

..........................................................................................................................................[2]

(j) Identify two further significant sources of error, other than the measurement of volume, in the experiments used for measuring temperature rise.

error 1 ..............................................................................................................................

..........................................................................................................................................

error 2 ..............................................................................................................................

..........................................................................................................................................[1]

(k) Complete the sections below.

(i) The maximum error in taking a temperature reading on a thermometer with

graduations at 1 °C is ………………°C.

(ii) The temperature rise when 30 cm3 of FA 2 is added to 10.00 cm3 of FA 1

is ………………°C.

(iii) Calculate the maximum percentage error due to the thermometer when measuring the temperature rise in (ii) above.

The maximum percentage error = ……………… %.[2]

[Total: 26]



6

9701/31/M/J/10© UCLES 2010

ForExaminer’s

Use

2 Solutions FA 3, FA 4 and FA 5 each contain a Group 2 halide. Solution FA 6 contains a potassium salt.

You will carry out tests to deduce the following. • the anion present in FA 6 • the solution containing the chloride ions • the solution containing barium ions

At each stage of any test you are to record details of the following. • colour changes seen • the formation of any precipitate and the colour of the precipitate


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted.

If any solution is warmed directly with a Bunsen burner a boiling-tube MUST be used. Rinse and reuse test-tubes where possible.

(a) Use information from the Qualitative Analysis Notes on page 11 to select a pair of reagents that, used together, identify the halide ion present.

The reagents are ……………………………..………… followed by ……………………………..………… . [1]

(b) Use your chosen reagents to carry out tests on FA 3, FA 4 and FA 5. Record your results in an appropriate form in the space below.

[2]

(c) From the results of the tests in (b) state which solution contains the chloride ion, Cl –.

Solution ………….. contains the chloride ion.

Explain the evidence that supports your conclusion.

..........................................................................................................................................

...................................................................................................................................... [1]



7


ForExaminer’s

Use

(d) Carry out the following tests on each of the solutions FA 3, FA 4 and FA 5. Record your observations below.

testobservations

FA 3 FA 4 FA 5

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous sodium hydroxide.

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous ammonia.

To 1 cm depth of solution in a test-tube, add 1 cm depth of FA 6.

[3]

(e) To 1 cm depth of FA 6 in a test-tube add 1 cm depth of dilute sulfuric acid.

observation

..........................................................................................................................................

...................................................................................................................................... [1]



8

9701/31/M/J/10© UCLES 2010

ForExaminer’s

Use

(f) From your observations in (d) and (e) you should be able to identify the anion in FA 6 and which of the solutions FA 3, FA 4 or FA 5 contains barium cations.

The anion present in FA 6 is ………………………. .

Ba2+ ions are contained in solution ………………………. .

Explain how your observations support your conclusions for

(i) the anion present in FA 6, .......................................................................................

.................................................................................................................................

(ii) the solution containing Ba2+ ions. ............................................................................

................................................................................................................................. [1]

Read through the remainder of question 2 before starting further practical work.

Heat a half-full 250 cm3 beaker of water for use as a hot water-bath.

(g) FA 7, FA 8, FA 9 and FA 10 are organic compounds. Each contains one of the following different functional groups.

• primary alcohol • tertiary alcohol • aldehyde • ketone

You are to react some of these compounds with some of the following reagents. • acidified aqueous potassium dichromate(VI) • 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent • ammoniacal silver nitrate (Tollens’ reagent)

You are provided with the first two reagents. You must prepare the last of these reagents, Tollens’ reagent, immediately before use. Follow the instructions in the box below.

To 2 cm depth of aqueous silver nitrate in a boiling-tube add ½ cm depth of aqueous sodium hydroxide. This will produce a brown precipitate of silver(I) oxide. Add aqueous ammonia a little at a time, with continuous shaking, until the brown precipitate just dissolves. Do not add an excess of aqueous ammonia.



9

9701/31/M/J/10© UCLES 2010

ForExaminer’s

Use

In each of the following tests add a few drops of the reagent to 1 cm depth of FA 7, FA 8, FA 9 and FA 10 in separate test-tubes.

In the tests using acidified potassium dichromate(VI) and Tollens’ reagent, if no initial reaction is seen, warm that tube and its contents in your hot water-bath. There is no need to heat any tube to which you have added 2,4-DNPH reagent.

Do not heat any tube with a naked flame.

Record your results in the table below.

Do not carry out tests for the shaded boxes.

reagentobservations

FA 7 FA 8 FA 9 FA 10

acidified potassium dichromate(VI)

2,4-DNPH reagent

Tollens’ reagent

[3]

(h) State which of the solutions contains a tertiary alcohol. Explain the observations leading to your conclusion.

FA …………… contains the tertiary alcohol.

explanation ......................................................................................................................

..........................................................................................................................................

State which of the solutions contains the aldehyde. Explain the observations leading to your conclusion.

FA …………… contains the aldehyde.

explanation ......................................................................................................................

.......................................................................................................................................... [2]

[Total: 14]



10

9701/31/M/J/10© UCLES 2010

Key: [ ppt. = precipitate. ]


ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.

ammonia produced on heating–

barium,

Ba2+(aq)no ppt. (if reagents are pure) no ppt.

calcium,

Ca2+(aq)white ppt. with high [Ca2+(aq)] no ppt.


grey-green ppt. soluble in excess

giving dark green solution

grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess

blue ppt. soluble in excess

giving dark blue solution

iron(II),Fe2+(aq)

green ppt. turning brown on contact with air

insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess


off-white ppt. rapidly turning brown on contact with air

insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




11

9701/31/M/J/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)

yellow solution turns orange with H+(aq);

gives yellow ppt. with Ba2+(aq);

gives bright yellow ppt. with Pb2+(aq)

chloride,

Cl– (aq)

gives white ppt. with Ag+(aq) (soluble in NH3(aq));

gives white ppt. with Pb2+(aq)

bromide,

Br– (aq)

gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq));


iodide,

I– (aq)

gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq));

gives yellow ppt. with Pb2+(aq)

nitrate,

NO3– (aq)

NH3 liberated on heating with OH-(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH-(aq) and Al foil;

NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids);

sulfite,

SO32– (aq)

SO2 liberated with dilute acids;

gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases







sulfur dioxide, SO2 turns acidified aqueous potassium dichromate(VI) from orange to green



12

9701/31/M/J/10© UCLES 2010

BLANK PAGE





This document consists of 14 printed pages and 2 blank pages.

DC (LEO/SW) 23111/3© UCLES 2010 [Turn over

*8263371454*







CHEMISTRY 9701/33


2 hours




1

2

Total

Session

Laboratory



2

9701/33/M/J/10© UCLES 2010

BLANK PAGE



3


ForExaminer’s

Use

1 You are required to determine the molar enthalpy change of solution for ammonium chloride, FA 1.

When an exothermic reaction takes place in a container such as a beaker, some of the evolved heat energy is absorbed by the beaker.

When an endothermic reaction takes place some of the required heat energy is supplied by the beaker.

The amount of heat energy evolved or supplied for a 1 °C change in temperature is known as the heat capacity of the beaker.

In preparation for your experiment to determine the molar enthalpy change of solution for FA 1 you will first need to determine the approximate heat capacity of a 250 cm3 beaker.

Before starting any practical work read through the instructions in (a) and draw up a table to record your results.



4

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(a) Determining the approximate heat capacity of the 250 cm3 beaker

When samples of hot and cold water are mixed in the 250 cm3 beaker, some heat is lost to the beaker in raising its temperature. To determine the approximate heat capacity of your 250 cm3 beaker, you will determine the maximum temperature rise when a sample of hot water is added to cold water in the beaker.

• Use a 50 cm3 measuring cylinder to transfer 50 cm3 of cold water into the 250 cm3

beaker. • Use the 50 cm3 measuring cylinder to transfer 50 cm3 of cold water into a 100 cm3

beaker. Note the temperature of the water in this 100 cm3 beaker and heat it carefully and gently until the temperature of the water in it has increased by 45–50 °C then stop heating, e.g. if the water is at 20.0 °C you should warm it to 65–70 °C.

• Stir the cold water in the 250 cm3 beaker with the thermometer. • Record the temperature of the cold water (this is the temperature at t = 0 min). • Record the temperature each minute for 3 minutes.

• After you have taken the reading at t = 3 min, use the thermometer to stir the hot water in the 100 cm3 beaker.

• At t = 4 min, measure the temperature of the hot water and record this value in the box below.

• Immediately add the hot water from the 100 cm3 beaker to the cold water in the 250 cm3 beaker. Stir with the thermometer but do not record the temperature.

• Continue to stir the water throughout the experiment. • Record the temperature at t = 5 min, and then every ½ minute until t = 8 min. • Empty and rinse the 250 cm3 beaker. Dry it using a paper towel. • Record all measurements of time and temperature obtained.

The temperature, T1, of the hot water at t = 4 min is ………… °C.

Table of results

[3]



5


ForExaminer’s

Use

(b) Graph plotting 1. Plot a graph of the temperature of the water in the 250 cm3 beaker (y-axis) against

time (x-axis) on the grid below. Do not plot the temperature, T1, of the hot water at t = 4 min. 2. Draw two straight lines of best fit; one through the points up to t = 3 min; the second

through the points from t = 5 min to t = 8 min. Extrapolate both lines to t = 4 min. 3. From the extrapolated lines read the minimum and the maximum temperatures at

t = 4 min. Record these values in the spaces provided below. 4. Determine the values for the two temperature changes at t = 4 min.

Minimum temperature, T2, at t = 4 min is ............... °C.

Maximum temperature, T3, at t = 4 min is ............... °C.

Temperature rise for 50 cm3 of cold water in the 250 cm3 beaker, (T3 – T2) is ............... °C.

Temperature fall for 50 cm3 of hot water from the 100 cm3 beaker, (T1 – T3) is ............... °C. [4]



6

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Calculations

Working should be shown in all calculations.

[4.2 J are absorbed or released when the temperature of 1.0 cm3 of water changes by 1.0 °C.]

(i) Calculate the heat energy gained by the 50 cm3 of cold water in the 250 cm3

beaker.

The heat energy gained by the cold water = ………… J.

(ii) Calculate the heat energy lost by the 50 cm3 of hot water from the 100 cm3 beaker.

The heat energy lost by the hot water = ………… J.

(iii) The difference between the values calculated in (i) and (ii) is an approximate value for the total heat energy absorbed by the 250 cm3 beaker during the experiment. The heat capacity of the beaker is the amount of heat energy absorbed for a 1 °C change in temperature.

approximate heat capacityof the 250 cm3 beaker

= (heat energy lost) – (heat energy gained)(T3 – T2)

J °C–1

Use your answers to (i) and (ii) and the temperature rise from (b) to calculate the approximate heat capacity of the 250 cm3 beaker.

The approximate heat capacity of the 250 cm3 beaker = ………… J °C–1.

[1]



7


BLANK PAGE



8

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(d) Determining the enthalpy change of solution for ammonium chloride

Follow the instructions below to find the temperature change when a known mass of solid ammonium chloride dissolves in water.

You are provided with two samples of ammonium chloride. You should use the sample labelled NH4Cl i n experiment 1 and the sample labelled FA 1 in experiment 2.

Experiment 1 • Enter all results in the table below. • Weigh the stoppered tube containing ammonium chloride, which is labelled

NH4Cl. • Use the 50 cm3 measuring cylinder to transfer 100 cm3 of cold water into the rinsed

and dried 250 cm3 beaker used in (a). • Stir the water in the beaker with the thermometer and record the temperature. • Add the solid from the weighed tube to the water. • Stir the mixture constantly with the thermometer. • Record the minimum temperature obtained in the solution. • Reweigh the tube labelled NH4Cl, its stopper and any residual ammonium

chloride. • Empty and rinse the beaker and dry it using a paper towel.

Experiment 2 • Enter all results in the table below. • Weigh a clean, dry, boiling-tube. • Weigh between 9.8 g and 10.2 g of FA 1, ammonium chloride, into the boiling-tube. • Repeat the procedure in experiment 1 and record the minimum temperature

obtained when this mass of FA 1 dissolves in 100 cm3 of water. • Reweigh the boiling-tube and any residual ammonium chloride.

Results

experiment 1 experiment 2

mass of tube + ammonium chloride / g

mass of empty tube / g

mass of tube + residual ammonium chloride / g

mass of ammonium chloride / g

initial temperature of water / °C

minimum temperature obtained / °C

temperature fall, ΔT / oC

[6]



9


ForExaminer’s

Use

(e) Calculations


(i) Use the temperature fall from (d), experiment 1, to calculate the change in heat energy of the solution.

[4.3 J are absorbed or released when the temperature of 1.0 cm3 of solution changes by 1.0 °C.]

The change in heat energy of the solution = ................. J.

(ii) To calculate the total change in heat energy as ammonium chloride dissolves in water, the change in heat energy of the 250 cm3 beaker has to be added to the change in heat energy of the solution.

Explain why these two changes in heat energy have to be added together.

..................................................................................................................................

..................................................................................................................................

..................................................................................................................................

(iii) Use your answer in (i) above and the approximate heat capacity of the 250 cm3 beaker calculated in (c)(iii) to calculate the combined change in heat energy of the beaker and solution.

The combined change in heat energy of the beaker and solution = ................. J.

(iv) Calculate how many moles of FA 1, NH4Cl, were used in (d), experiment 1. [Ar; Cl, 35.5; H, 1.0; N, 14.0]

………… mol of FA 1 were used in experiment 1.

i

ii

iii

iv



10

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(v) Calculate the enthalpy change when 1 mol of FA 1 dissolves in an excess of water.This is the molar enthalpy change of solution, ΔHsolution (NH4Cl ).

Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHsolution (NH4Cl ) = ........ ............................ kJ mol–1.

sign calculated value

(vi) Explain the significance of the sign you have given in (v) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [8]

v

vi

vii

viii



11


ForExaminer’s

Use

(f) Evaluation

A data book value for the molar enthalpy change of solution, ΔHsolution (NH4Cl ), is +15.2 kJ mol–1.

The value you have obtained may be significantly different from this value.

Calculate the difference between your value of ΔHsolution (NH4Cl ) and the data book value. Record this difference below. Express this difference as a percentage of the data book value.

difference = ……………….. kJ mol–1

percentage difference = ……………….. % [1]

(g) Sources of error

Describe one major source of error in this experiment. Suggest an improvement which would significantly increase the accuracy of the experiment. Explain why your suggestion would produce a more accurate value.

description of major source of error

.........................................................................................................................................

.........................................................................................................................................

suggested improvement

.........................................................................................................................................

.........................................................................................................................................

explanation of why suggestion would increase experimental accuracy

.........................................................................................................................................

......................................................................................................................................... [2]

[Total: 25]



12

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

2 (a) You are provided with three solutions, FA 2, FA 3 and FA 4. The only anions that may be present in these solutions are sulfate and carbonate. One or more of the solutions may contain both anions.

Identification of the anions in FA 2, FA 3 and FA 4.

Most metal carbonates are insoluble, most metal sulfates are soluble and all metal nitrates are soluble in water.

(i) Use this information and the Qualitative Analysis Notes on page 16 to select • reagent 1, to identify any carbonate ion present, • reagent 2, to identify any sulfate ion present.

reagent 1 ............................................. reagent 2 ............................................. [1]

(ii) Explain the order in which you will add your chosen reagents to determine the anion or anions present in each of FA 2, FA 3 and FA 4.

..................................................................................................................................

..................................................................................................................................

..............................................................................................................................[1]

(iii) Use the reagents selected in (a)(i) to test each of the solutions FA 2, FA 3 and FA 4. Record your observations in the table below.

reagentobservations

FA 2 FA 3 FA 4

[2]

(iv) From your observations, identify the anion or anions present in each of the solutions.

solution carbonate sulfate evidence

FA 2

FA 3

FA 4

[2]



13


ForExaminer’s

Use

(b

) Yo

u ar

e pr

ovid

ed w

ith fo

ur s

olut

ions

, FA

5, F

A 6

, FA

7 a

nd F

A 8

. Per

form

the

test

-tub

e ex

perim

ents

des

crib

ed b

elow

and

reco

rd y

our o

bser

vatio

ns

in th

e ta

ble.

Whe

re g

ases

are

rel

ease

d th

ey s

houl

d be

iden

tifie

d by

a te

st, d

escr

ibed

in t

he

app

rop

riat

e p

lace

in y

ou

r o

bse

rvat

ion

s.

test

sob

serv

atio

ns

FA 5

FA 6

FA 7

FA 8

(i)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

test

-tub

e,

add

10 d

rops

of a

queo

us s

odiu

m h

ydro

xide

.S

hake

the

mix

ture

,

then

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

sodi

um h

ydro

xide

.S

hake

the

mix

ture

aga

in,

then

leav

e th

e tu

be to

sta

nd fo

r 2–

3 m

inut

es.

(ii)

If no

pre

cipi

tate

has

form

ed in

test

(i)

abo

ve;

tran

sfer

the

solu

tion

to a

bo

ilin

g-t

ub

e an

d w

arm

gen

tly w

ith a

Bun

sen

burn

er.

Car

e: h

eati

ng

aq

ueo

us

sod

ium

hyd

roxi

de

in a

tu

be

may

cau

se t

he

solu

tio

n t

o b

e ej

ecte

d f

rom

th

e tu

be.

(iii)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

test

-tub

e,

add

10 d

rops

of a

queo

us a

mm

onia

.S

hake

the

mix

ture

,

then

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

amm

onia

.S

hake

the

mix

ture

aga

in,

then

leav

e th

e tu

be to

sta

nd fo

r 2–

3 m

inut

es.

[7

]

i

ii

iii

iv

v

vi

vii



14

9701/33/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) From your observations in (b), identify the cation present in each of the following solutions.

solution cation evidence

FA 5

FA 6

FA 8

[2]

[Total: 15]



15

9701/33/M/J/10© UCLES 2010




ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




16

9701/33/M/J/10© UCLES 2010




ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)

NH3 liberated on heating with OH–(aq) and Al foil;


sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid) or gives white ppt. with Pb2+(aq)

sulfite,

SO32– (aq)


gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid)

3 Tests for gases











DC (SJF5449/CGW) 11614/4© UCLES 2010 [Turn over

*1626130202*







CHEMISTRY 9701/34


2 hours




1

2

Total

Session

Laboratory



2

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use


You are provided with the following reagents. • weighing bottles/tubes labelled FB 1, FB 2 and FB 3; each containing a different mass

of sodium hydrogencarbonate, NaHCO3 • additional solid sodium hydrogencarbonate (approximately 10 g) • FB 4, 3 .0 mol dm–3 hydrochloric acid, HCl

The reaction of sodium hydrogencarbonate with hydrochloric acid is endothermic.

By measuring the maximum temperature decrease when the different masses of sodium hydrogencarbonate react with hydrochloric acid you are to determine the enthalpy change of neutralisation for 1 mol of NaHCO3 with HCl.

(a) Method

• Weigh the bottle/tube containing the sodium hydrogencarbonate labelled FB 1. • Support the plastic cup in the 250 cm3 beaker. • Use the measuring cylinder to transfer 30 cm3 of FB 4 into the plastic cup. • Place the thermometer in the acid in the plastic cup and record the steady

temperature of the acid. • Add the contents of the weighed tube, FB 1, to the acid in the plastic cup, a little at

a time with constant stirring. • You should add the solid as quickly as possible – taking care to minimise any acid

spray from the plastic cup. Avoid breathing any fumes from the experiment. • Record the minimum temperature obtained in the reaction. • Reweigh the emptied tube, FB 1, containing any remaining solid that was not tipped

from the tube. • Empty and rinse the plastic cup. Rinse the thermometer. Shake dry the plastic cup. • Repeat the experiment using tubes labelled FB 2 and FB 3. In each experiment

use 30 cm3 of FB 4.

Carry out two further experiments. Using the empty weighing bottles/tubes, labelled FB 5 and FB 6, weigh two further

masses of sodium hydrogencarbonate. Choose masses to enable you to plot an appropriate graph of temperature change against mass of sodium hydrogencarbonate.

Results Record your results in an appropriate form showing, for each experiment, the

measurements of mass and temperature and the calculated temperature fall.

[9]

i

ii

iii

iv

v

vi

vii

viii

ix



3


ForExaminer’s

Use

(b) Use the grid below to plot a graph of decrease in temperature (y-axis) against the mass of sodium hydrogencarbonate added (x-axis).

Draw a line of best fit through the plotted points. You should consider if the best-fit line passes through the origin (0,0) of the graph.

[4]

i

ii

iii

iv



4

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Explain why the mass of NaHCO3 is plotted on the x-axis rather than on the y-axis.

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Construct the balanced equation for the reaction of NaHCO3 with hydrochloric acid.

..................................................................................................................................... [1]

(e) Calculate the gradient of your graph. Show all of your working clearly, both construction lines on the graph and working in the

calculation.

[3]

(f) Although there is insufficient acid in 30 cm3 of FB 4 to neutralise 1 mol of NaHCO3 it is possible to calculate the theoretical fall in temperature for this reaction.

Use your answer from (e) to calculate this value. [Ar: C, 12.0; H, 1.0; Na, 23.0; O, 16.0]

The theoretical fall in temperature for 1 mol of NaHCO3 = ………………………. °C [1]

(g) Calculate the theoretical enthalpy change for the neutralisation of 1 mol of NaHCO3 by hydrochloric acid. Give your answer in kJ mol–1 and include the correct sign for the reaction.

[4.3 J are absorbed or released when the temperature of 1 cm3 of solution changes by 1 °C.]

ΔH = ……………………… kJ mol–1 [2]



5


ForExaminer’s

Use

(h) Suggest two ways in which your apparatus could be modified to reduce transfer of heat from the surroundings to the solution in the apparatus.

modification 1 ..................................................................................................................

.........................................................................................................................................

modification 2 ..................................................................................................................

..................................................................................................................................... [1]

(i) State and explain why the experiment would be more accurate if the volumes of FB 4 had been measured using a burette instead of a measuring cylinder.

.........................................................................................................................................

..................................................................................................................................... [1]

(j) The mass of NaHCO3 used in a further experiment and its associated temperature change are shown in the tables below.

• The mass was obtained on a balance reading to 1 decimal place. • The thermometer used was graduated at 1 °C.

Complete the table to show the errors in these results.

mass of NaHCO3 5.6 g temperature change –12.0 °C

maximum error in a single balance reading ± ………… g

maximum error in a single thermometer reading ± ………… °C

% error in measured mass ………… %

% error in temperature change ………… %

[2]

(k) Two students add 6.0 g of sodium carbonate to 50.00 cm3 of 2.0 mol dm–3 hydrochloric acid. Each student repeats the experiment a number of times.

The thermometer readings and temperature changes obtained consistently by each student are shown below.

initial temperature / °C

final temperature / °C

temperature rise/ °C

student 1 20.0 28.0 8.0

student 2 19.0 27.0 8.0

Suggest the type of error shown by these results.

..................................................................................................................................... [1]

[Total: 26]



6

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

2 FB 7 and FB 8 are aqueous solutions of salts. One of these contains two cations and one anion.

The other contains one cation and one anion. Both FB 7 and FB 8 have a common cation.

You will carry out tests to deduce the following. • the cations present in each solution • whether a sulfate ion is present in either solution

At each stage of any test you are to record details of the following. • colour changes seen • the formation of any precipitate and the colour of the precipitate


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed directly with a Bunsen burner a boiling-tube MUST be used.

Rinse and reuse test-tubes where possible.

(a) Use information from the Qualitative Analysis Notes on page 11 to select a pair of reagents that, used together, determine whether a sulfate ion is present in either solution.

The reagents are …………………………………………

followed by ………………………………………… . [1]

(b) Use your chosen reagents to carry out tests on FB 7 and FB 8. Record your results in an appropriate form in the space below.

[2]



7


ForExaminer’s

Use

(c) From your observations in (b) show with a tick which of the following statements is true.

FB 7 contains the sulfate ion

FB 8 contains the sulfate ion

neither solution contains the sulfate ion

Explain the evidence that supports your conclusion.

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Carry out the following tests on the solutions FB 7 and FB 8. Record your observations below.

test observations

FB 7 FB 8

To 1 cm depth of solution in a boiling-tube, add 2 cm depth of aqueous sodium hydroxide;then

warm the solution gently.

Care is needed when heating aqueous sodium hydroxide.

To 1 cm depth of solution in a test-tube, add 2 cm depth of aqueous ammonia.

[3]

(e) To 1 cm depth of FB 7 in a test-tube add 1 cm depth of sodium hydroxide. Leave to stand for a few minutes.

observation

.........................................................................................................................................

..................................................................................................................................... [1]



8

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

(f) From your observations in (d) and (e) you should be able to identify the common cation in the solutions and the second cation in one of the solutions.

The common cation present in both solutions is ………………………. .

The second cation contained in one of the solutions is ………………………. .

Explain how your observations support your conclusions for

(i) the common cation,

.................................................................................................................................

.................................................................................................................................

(ii) the second cation.

.................................................................................................................................

................................................................................................................................. [1]

Read through the remainder of question 2 before starting further practical work. Heat a half-full 250 cm3 beaker of water for use as a hot water-bath.

(g) FB 9, FB 10, FB 11 and FB 12 are organic compounds. Each contains one of the following different functional groups.

• primary alcohol • secondary alcohol • aldehyde • ketone

You are to react each of these compounds with some of the following reagents. • acidified aqueous potassium dichromate(VI) • 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent • ammoniacal silver nitrate (Tollens’ reagent)

You are provided with the first two reagents. You must prepare the last of these reagents, Tollens’ reagent, immediately before use. Follow the instructions in the box below.

To 2 cm depth of aqueous silver nitrate in a boiling-tube add ½ cm depth of aqueous sodium hydroxide. This will produce a brown precipitate of silver(I) oxide. Add aqueous ammonia a little at a time, with continuous shaking, until the brown precipitate just dissolves. Do not add an excess of aqueous ammonia.



9

9701/34/M/J/10© UCLES 2010

ForExaminer’s

Use

In each of the following tests add a few drops of the reagent to 1 cm depth of FB 9, FB 10, FB 11 and FB 12 in separate test-tubes.

In the tests using acidified potassium dichromate(VI) and Tollens’ reagent, if no initial reaction is seen, warm that tube and its contents in your hot water-bath. There is no need to heat any tube to which you have added 2,4-DNPH reagent.

Do not heat any tube with a naked flame.

Record your results in the table below.

Do not carry out tests for the shaded boxes.

reagentobservations

FB 9 FB 10 FB 11 FB 12

acidified potassium dichromate(VI)

2,4-DNPH reagent

Tollens’ reagent

[3]

(h) State which of the solutions contain alcohols. Explain the observations leading to your conclusion.

FB …………… and FB …………… contain alcohols.

explanation .....................................................................................................................

.........................................................................................................................................

State which solution contains the ketone. Explain the observations leading to your conclusion.

FB …………… contains the ketone.

explanation .....................................................................................................................

......................................................................................................................................... [2]

[Total: 14]



10

9701/34/M/J/10© UCLES 2010



ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




11

9701/34/M/J/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)

NH3 liberated on heating with OH-(aq) and Al foil

nitrite,

NO2– (aq)

NH3 liberated on heating with OH-(aq) and Al foil;


sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids);

sulfite,

SO32– (aq)


gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)

3 Tests for gases










12

9701/34/M/J/10© UCLES 2010

BLANK PAGE






DC (LEO/SW) 23108/2© UCLES 2010 [Turn over

*5803539249*







CHEMISTRY 9701/35


2 hours




1

2

Total

Session

Laboratory



2

9701/35/M/J/10© UCLES 2010

BLANK PAGE



3


ForExaminer’s

Use

1 You are required to find the molar enthalpy change for the decomposition of sodium hydrogencarbonate, NaHCO3.

NaHCO3 ½Na2CO3 + ½H2O + ½CO2

FA 1 is anhydrous sodium hydrogencarbonate. FA 2 is anhydrous sodium carbonate. FA 3 i s 4.0 mol dm–3 hydrochloric acid.

You will determine the value for the molar enthalpy change of neutralisation for each of FA 1 and FA 2, using an excess of FA 3. You will then use these values to calculate the molar enthalpy change for the decomposition of sodium hydrogencarbonate.

Warning: 4.0 mol dm–3 hydrochloric acid is an irritant. Very rapid effervescence occurs when FA 1 or FA 2 are added to FA 3.

For safe working, and to minimize the formation of ‘acid mist’, the solid must be added carefully, with stirring, to the acid. See further instructions below.

Before starting any practical work read through the instructions in (a) and draw up two tables to record your results.



4

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(a) Determining the molar enthalpy change of neutralisation between FA 1 and FA 3

NaHCO3 + HCl NaCl + H2O + CO2

Follow the instructions below to determine the temperature change when a known mass of FA 1, sodium hydrogencarbonate, reacts with an excess of FA 3, hydrochloric acid.

• Weigh the stoppered tube labelled FA 1 containing sodium hydrogencarbonate. • Use a 50 cm3 measuring cylinder to transfer 50 cm3 of FA 3 into a 250 cm3 beaker. • Stir the acid in the beaker with the thermometer. Record the temperature of the

acid; this is the temperature at t = 0 min. • Record the temperature each minute for 3 minutes. • At t = 4 min, start to carefully add the weighed sample of FA 1 to the acid. • Add the solid in at least 4 or 5 portions to prevent excessive effervescence. • While adding the solid stir the mixture constantly with the thermometer, but do not

record the temperature. • Continue to stir the mixture throughout the experiment. • Record the temperature at t = 5 min, then every ½ minute until t = 8 min. • Reweigh the tube labelled FA 1, its stopper and any residual sodium

hydrogencarbonate. • Empty and rinse the beaker and dry it using a paper towel. • In one of your tables record the balance readings and the mass of FA 1 added;

in the second table record all measurements of time and temperature.

Table of results

[3]



5


ForExaminer’s

Use

(b) Graph plotting

1. Plot a graph of temperature (y-axis) against time (x-axis) on the grid below. 2. Draw two straight lines of best fit; one through the points up to t = 3 min; the second

through the points from t = 5 min to t = 8 min. Extrapolate both lines to t = 4 min. 3. From the extrapolated lines read the minimum and the maximum temperatures at

t = 4 min. Record these values in the spaces provided below. 4. Determine the value for the temperature fall at t = 4 min.

The minimum temperature at t = 4 min is …………. °C.

The maximum temperature at t = 4 min is ………… °C.

The temperature fall, ΔT1, at t = 4 min is ………… °C. [4]



6

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) Calculations


(i) Use the equation below and the temperature fall, ΔT1, from (b) to calculate the change in heat energy during the reaction of FA 1 with FA 3.

change in heat energy = 50 × 4.3 × ΔT1

The change in heat energy = .................. J.

(ii) Calculate how many moles of FA 1, NaHCO3, were used in your experiment. [Ar; C, 12.0; H, 1.0; O, 16.0; Na, 23.0]

.................. mol of FA 1 were used in the experiment.

(iii) Calculate the enthalpy change when 1 mol of FA 1 reacts with an excess of the hydrochloric acid, FA 3.

This is the molar enthalpy change of neutralisation, ΔHneutralisation (NaHCO3). Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHneutralisation(NaHCO3) = ........ ............................ kJ mol–1.


(iv) Explain the significance of the sign you have given in (iii) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [3]



7


BLANK PAGE



8

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(d) Determining the molar enthalpy change of neutralisation between FA 2 and FA 3

Na2CO3 + 2HCl 2NaCl + H2O + CO2

Follow the instructions below to find the temperature change when a known mass of FA 2, sodium carbonate, reacts with an excess of FA 3, hydrochloric acid.

You are provided with two samples of sodium carbonate. You should use the sample labelled Na2CO3 in experiment 1 and the sample labelled FA 2 in experiment 2.

Experiment 1 • Enter all results in the table below. • Weigh the stoppered tube containing sodium carbonate, which is labelled Na2CO3. • Use a 50 cm3 measuring cylinder to transfer 50 cm3 of FA 3 into the rinsed and

dried 250 cm3 beaker used in (a). • Stir the acid in the beaker with the thermometer and record the temperature. • Start to add carefully the weighed sample of Na2CO3 to the acid. • As in the experiment in (a), add the solid in at least 4 or 5 portions to prevent

excessive effervescence. • While adding the solid stir the mixture constantly with the thermometer. • Record the maximum temperature obtained during the reaction. • Reweigh the tube labelled Na2CO3, its stopper and any residual sodium

carbonate. • Empty and rinse the beaker and dry it using a paper towel.

Experiment 2 • Enter all results in the table below. • Weigh a clean, dry, boiling-tube. • Weigh between 7.0 g and 7.5 g of FA 2, sodium carbonate, into the boiling-tube. • Repeat the procedure in experiment 1 and record the maximum temperature

obtained when this mass of FA 2 reacts with 50 cm3 of FA 3. • Reweigh the boiling-tube and any residual sodium carbonate.

Results


mass of tube + anhydrous sodium carbonate / g

mass of empty tube / g

mass of tube + residual sodium carbonate / g

mass of anhydrous sodium carbonate / g

initial temperature of acid / oC

maximum temperature obtained / oC

temperature rise, ΔT2 / oC

[6]



9


ForExaminer’s

Use

(e) Calculations


(i) Use the equation below and the temperature rise, ΔT2, from (d) for experiment 1 to calculate the change in heat energy during the reaction of sodium carbonate with FA 3.

change in heat energy = 50 × 4.3 × ΔT2

Change in heat energy = .................. J.

(ii) Calculate how many moles of sodium carbonate were used in your experiment 1. [Ar; C, 12.0; O, 16.0; Na, 23.0]

.................. mol of sodium carbonate were used in experiment 1.

(iii) Calculate the enthalpy change when 1 mol of sodium carbonate reacts with an excess of the hydrochloric acid, FA 3.

This is the molar enthalpy change of reaction, ΔHneutralisation(Na2CO3). Make certain that your answer is given in kJ mol–1 and has the appropriate sign.

ΔHneutralisation(Na2CO3) = ........ ............................ kJ mol–1.


(iv) Explain the significance of the sign you have given in (iii) and how it is related to your experimental results.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [5]



10

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(f) Calculating the enthalpy change of decomposition of FA 1, ΔHdecomposition(NaHCO3)

Use your values for ΔHneutralisation (NaHCO3) and ΔHneutralisation (Na2CO3) in the expression below to calculate a value for the molar enthalpy change of decomposition, ΔH decomposition (NaHCO3), for FA 1.

ΔH decomposition (NaHCO3) = ΔHneutralisation (NaHCO3) – ½ΔHneutralisation (Na2CO3)

ΔHdecomposition(NaHCO3) = ........ ............................ kJ mol–1.

sign calculated value [1]

(g) Evaluation

An alternative method for the determination of ΔHdecomposition (NaHCO3) gave a value of +42. 5 kJ mol–1.

The value you have obtained may be significantly different from this value.

Calculate the difference between your value of ΔHdecomposition (NaHCO3) and that obtained by the alternative method.

Record this difference below. Express this difference as a percentage of the alternative value.

difference = ………………. kJ mol–1

percentage difference = ……………….. % [1]

(h) Sources of error

Describe one major source of error in this experiment. Suggest an improvement which would significantly increase the accuracy of the experiment. Explain why your suggestion would produce a more accurate value.

description of major source of error

.........................................................................................................................................

.........................................................................................................................................

suggested improvement

.........................................................................................................................................

.........................................................................................................................................

explanation of why suggestion would increase experimental accuracy

.........................................................................................................................................

......................................................................................................................................... [2]

[Total: 25]



11


ForExaminer’s

Use

2 (a) You are provided with three solutions, FA 4, FA 5 and FA 6. The only anions that may be present in these solutions are carbonate and chloride. One or more of the solutions may contain both anions.

Identification of the anions in FA 4, FA 5 and FA 6

Most metal carbonates are insoluble, most metal chlorides are soluble and all metal nitrates are soluble in water.

(i) Use this information and the Qualitative Analysis Notes on page 15 to select • reagent 1, to identify any carbonate ion that is present, • reagent 2, to identify any chloride ion present.

reagent 1 ............................................. reagent 2 ............................................. [1]

(ii) Explain the order in which you will add your chosen reagents to determine the anion or anions present in each of FA 4, FA 5 and FA 6.

..................................................................................................................................

..................................................................................................................................

............................................................................................................................. [1]

(iii) Use the reagents selected in (a)(i) to test each of the solutions FA 4, FA 5 and FA 6. Record your observations in the table below.

reagentobservations

FA 4 FA 5 FA 6

[2]

(iv) From your observations, identify the anion or anions present in each of the solutions.

solution carbonate chloride evidence

FA 4

FA 5

FA 6

[2]



12

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(b

) Yo

u ar

e pr

ovid

ed w

ith f

our

solu

tions

, FA

7,

FA 8

, FA

9 a

nd F

A 1

0. P

erfo

rm t

he t

est-

tube

exp

erim

ents

des

crib

ed b

elow

and

rec

ord

your

ob

serv

atio

ns in

the

tabl

e.

test

sob

serv

atio

ns

FA 7

FA 8

FA 9

FA 1

0

(i)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

te

st-t

ube,

add

5 d

rops

of a

queo

us s

odiu

m

hydr

oxid

e, s

hake

the

mix

ture

then

,

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

sodi

um h

ydro

xide

.

(ii)

To a

bout

1 c

m d

epth

of s

olut

ion

in a

te

st-t

ube,

add

10

drop

s of

aqu

eous

am

mon

ia, s

hake

the

mix

ture

then

,

add

a fu

rthe

r 2

cm d

epth

of a

queo

us

amm

onia

.

(iii)

Sel

ect a

rea

gent

that

will

con

firm

the

iden

tity

of a

ny io

ns p

rodu

cing

whi

te p

reci

pita

tes

in b

oth

of th

e te

sts

abov

e.To

abo

ut 1

cm

dep

th o

f sol

utio

n in

a te

st-t

ube

add

the

sele

cted

rea

gent

. Rec

ord

the

appr

opria

te o

bser

vatio

ns b

elow

.

Th

e re

agen

t is

[7

]

i

ii

iii

iv

v

vi

vii



13

9701/35/M/J/10© UCLES 2010

ForExaminer’s

Use

(c) From your observations, identify the cation present in each of the following solutions.

solution cation evidence

FA 7

FA 9

FA 10

[2]

[Total: 15]



14

9701/35/M/J/10© UCLES 2010




ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




15

9701/35/M/J/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid) or gives white ppt. with Pb2+(aq)

sulfite,

SO32– (aq)



3 Tests for gases










16

9701/35/M/J/10© UCLES 2010

BLANK PAGE





This question paper consists of 7 printed pages and 1 blank page.

SP (SM) S25940/2© CIE 2002 [Turn over

CAMBRIDGE INTERNATIONAL EXAMINATIONS

General Certificate of Education Advanced Level

CHEMISTRY 9701/3PAPER 3 Practical Test

OCTOBER/NOVEMBER SESSION 20021 hour 15 minutes

Candidates answer on the question paper.Additional materials:

As listed in Instructions to SupervisorsElectronic calculator and/or Mathematical tables

TIME 1 hour 15 minutes

INSTRUCTIONS TO CANDIDATES

Write your name, Centre number and candidate number in the spaces at the top of this page.

Answer all questions.

Write your answers in the spaces provided on the question paper.

INFORMATION FOR CANDIDATES

The number of marks is given in brackets [ ] at the end of each question or part question.

You may use a calculator.

You are advised to show all working in calculations.

Use of a Data Booklet is unnecessary.

Qualitative analysis notes are printed on pages 6 and 7.

FOR EXAMINER’S USE

1

2

TOTAL

CandidateCentre Number Number

Candidate Name



2

9701/3/O/N/02

1 FA 1 is a hydrated metal sulphate, XSO4.7H2O.

You are required to determine the mass of water of crystallisation (the 7H2O in the formulaabove) in a weighed sample of FA 1 and to calculate the relative atomic mass, Ar, of theelement X.

(a) Accurately weigh the hard glass test-tube provided. Record the mass in Table 1.1 below.

Add to the test-tube between 2.00 g and 2.50 g of FA 1 and accurately weigh the test-tube and contents. Record this mass in Table 1.1 below.

Table 1.1 Mass of FA 1

(b) Heat the test-tube, gently at first then strongly, to drive off the water of crystallisation.The crystals will ‘crackle’ at first as water is lost and ‘steam’ (condensed water vapour)will be seen coming out of the mouth of the tube.

If the crystals are overheated the sulphate can decompose and give off sulphur trioxidewhich will be seen as white fumes. If you see white fumes, do not confuse this withsteam, stop heating.

Place the test-tube on a heat proof mat and leave to cool. Do not move about thelaboratory with a hot test-tube.

(You are advised to continue with the second question while the tube cools.)

When cool, reweigh the test-tube and its contents. Record the mass in Table 1.2 below.

Table 1.2 Mass of FA 1 after heating

(c) By repeating the heating, cooling and reweighing, show clearly by your results inTable 1.2 that all the water of crystallisation has been driven from the crystals, FA 1.

[4]

Accuracy [6]

ForExaminer’s

Use

Mass of test-tube + FA 1 / g

Mass of empty test-tube / g

Mass of FA 1 / g

Mass of test-tube + FA 1 after heating / g

Mass of empty test-tube (from Table 1.1) / g

Mass of FA 1 after heating / g



3

9701/3/O/N/02 [Turn over

(d) Calculate

(i) the mass of anhydrous XSO4 present in the crystals.

(ii) the mass of water driven from the crystals of FA 1.

[1]

(e) Calculate how many moles of water are present in the sample of FA 1 used.[Ar; H, 1.0; O, 16.0.]

[1]

(f) Use your answer to (e) and the formula XSO4.7H2O to calculate how many moles ofXSO4 are present in the sample of FA 1 used.

[1]

(g) Use your answers to (d) and (f) to calculate the relative molecular mass, Mr, of XSO4.

[1]

(h) Calculate the relative atomic mass, Ar, of the element X.[Ar; O, 16.0; S, 32.0.]

[1]

[Total : 15]

ForExaminer’s

Use



4

9701/3/O/N/02

2 The solution FA 2 contains two cations and two anions from the following list: (Al3+, NH4+,

Ba2+, Ca2+, Cr3+, Cu2+, Fe2+, Fe3+, Pb2+, Mg2+, Mn2+, Zn2+; CO32–, CrO4

2–, Cl–, Br–, I–,NO3

–, NO2–, SO4

2–, SO32–).

In all tests, the reagent should be added gradually until no further change is observed,with shaking after each addition.Record your observations and the deductions you make from them in the spacesprovided.Your answers should include• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.

You should indicate clearly at what stage in a test a change occurs, writing anydeductions you make alongside the observations on which they are based.


Candidates are reminded that definite deductions may be made from testswhere there appears to be no reaction.

ForExaminer’s

Use

Test Observations [5] Deductions [4]

(a) Place 3 cm depth of FA 2in a boiling-tube, add anequal depth of diluteaqueous sodiumhydroxide.

Cautiously warm thetube.

(b) Filter the mixture from (a)and collect the filtrate.

Leave the residue in thefilter paper and observeit again after severalminutes.

(c) Place 2 cm depth of thefiltrate from (b) in a test-tube and add dilutenitric acid, drop by drop,until no further changeis seen.



5


Summary

The cations present in FA 2 are …………… and ……………

The anions in FA 2 are …………… and ……………[1]

[Total : 10]

ForExaminer’s

Use

Test Observations Deductions

(d) Place 2 cm depth of thefiltrate from (b) in aboiling-tube. Add apiece of aluminium foil.


(e) Place 3 cm depth of FA 2in a test-tube, add anequal depth of diluteaqueous ammonia.


Filter the mixture. Adddilute nitric acid, drop bydrop, to the filtrate until nofurther change is seen.

(f) Place 2 cm depth of FA 2in a test-tube, add dilutehydrochloric acid,

followed by aqueousbarium chloride.

(g) Place 2 cm depth of FA 2in a test-tube, add dilutenitric acid,

followed by aqueoussilver nitrate.



6

9701/3/O/N/02


[Key: ppt. = precipitate.]



aluminium,Al3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)















grey-green ppt. soluble in excess givingdark green solution





no ppt.

no ppt.





7

9701/3/O/N/02


3 Tests for gases

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction









gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilutestrong acid)








ammonia, NH3

carbon dioxide, CO2

chlorine, Cl2

hydrogen, H2

oxygen, O2




8

9701/3/O/N/02

BLANK PAGE




SP (AT) S39107/4© UCLES 2003 [Turn over

CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education


CHEMISTRY 9701/03

Paper 3 Practical TestOctober/November 2003

1 hour 15 minutesCandidates answer on the Question Paper.Additional materials: as listed in Instructions to Supervisors.


Write your name and details, including examination session and laboratory where appropriate, in the boxesprovided.Write in dark blue or black pen in the spaces provided on the Question Paper.You may use a pencil for any diagrams, graphs, or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.



1

2

TOTAL



SESSION

LABORATORY



2

9701/3/O/N/03

1

Weigh the empty boiling-tube labelled X and record the mass in Table 1.1.

Transfer approximately half of the ‘washing soda’ crystals, FA 1, from boiling-tube Y intoboiling-tube X. Keep the remaining solid for use in Question 2.

Reweigh the boiling-tube X and FA 1 and record the mass in Table 1.1

Table 1.1

[6]

Gently heat the crystals in the tube. The solid will dissolve into the water contained in thecrystals.Continue the gentle heating until all the water has evaporated and solid remains in the tube.Take care to avoid any loss of material during this initial heating.Warm the upper parts of the boiling-tube to evaporate any water that may have condensed

there.When all the water has evaporated heat the solid strongly to drive off any remaining water.Allow the boiling-tube to cool, reweigh and record the mass in Table 1.1.

Reheat, cool and reweigh the boiling-tube and its contents. Record the mass in Table 1.1.

(a) How can you be sure that all of the water has been driven off from the crystals?

[1]

(b) Calculate the mass of crystals at the start of the experiment.

[1]

You are advised to start on Question 2 while the tube cools.

‘Washing soda’ is made from crystals of sodium carbonate, which contain 62.94%water and 37.06% sodium carbonate.

When stored, these crystals lose some of the water in the crystals to theatmosphere.

You are to determine in two separate experiments the amount of water that hasbeen lost to the atmosphere.

ForExaminer’s

Use

Mass of empty boiling-tube X / g

Mass of boiling-tube X + FA 1 before heating / g

Mass of boiling–tube X + solid after heating / g

Mass of boiling–tube X + solid after re-heating / g

Mass of anhydrous Na2CO3 left after heating / g



3


(c) Calculate the mass of water driven from the crystals.

[1]

(d) What is the percentage of water in your sample of FA 1?

[1]

[Total : 10]

ForExaminer’s

Use



4

9701/3/O/N/03

2 FA 1 is solid ‘washing soda’, originally sodium carbonate decahydrate, Na2CO3.10H2O.FA 2 is 0.100 mol dm–3 hydrochloric acid, HCl.

Weigh a 100 cm3 beaker. Record the mass in Table 2.1.Tip the remaining FA 1 from tube Y into the beaker and weigh the beaker and crystals.

Table 2.1

[1]

Add distilled water to the beaker to dissolve the crystals. Carefully transfer the solution to a250 cm3 graduated (volumetric) flask. Rinse the beaker several times adding the rinse waterto the graduated flask.

Make the solution up to 250 cm3 with distilled water and invert a number of times to ensurethorough mixing. Label this solution FA 3.

Pipette 25.0 cm3 of FA 3 into a conical flask and add a few drops of the indicator provided.Titrate the solution with FA 2, contained in a burette. Record your results in Table 2.2.

Repeat the titration as many times as you think necessary to obtain accurate results. Make certain that the recorded results show the precision of your practical work.


[2] + [6]

The indicator used was.............................................................................................................

Summary


Show which results you used to obtain this volume of FA 2 by placing a tick (✓) under thereadings in Table 2.2.

ForExaminer’s

Use

Mass of beaker / g

Mass of beaker + FA 1 / g

Mass of FA 1 / g

Final burette reading / cm3

Initial burette reading / cm3




5

9701/3/O/N/03

(a) Calculate the number of moles of hydrochloric acid run from the burette.

[1](b) Sodium carbonate reacts with hydrochloric acid

Na2CO3 + 2HCl → 2NaCl + CO2 + H2O

Calculate the number of moles of sodium carbonate, Na2CO3, in 250 cm3 of FA 3.

[2]

(c) Calculate the mass of sodium carbonate, Na2CO3, dissolved in 250 cm3 of FA 3.[Na, 23.0; C, 12.0; O, 16.0.]

[1]

(d) Calculate the mass of water present in the washing soda crystals.

[1]

(e) Calculate the percentage (%) of water in the sodium carbonate crystals, FA 1.

[1]

[Total : 15]

ForExaminer’s

Use



6

9701/3/O/N/03

BLANK PAGE



7

9701/3/O/N/03

BLANK PAGE



8

9701/3/O/N/03

BLANK PAGE




MML 6133 6/03 S66582/1© UCLES 2004 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education


CHEMISTRY 9701/03





Answer all questions.At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.





LABORATORY

SESSION

1

2

TOTAL



© UCLES 2004

2

9701/03/O/N/04

ForExaminer's

Use

1 FA 1 is an aqueous solution containing 23.72 g dm–3 of sodium thiosulphate, Na2S2O3.FA 2 is a solution of an oxidant, X, containing 5.15 g dm–3 of X.FA 3 is a solution containing potassium iodide, KI.FA 4 is 1.00 mol dm–3 sulphuric acid, H2SO4.

In the presence of acid, the oxidant X oxidises iodide ions to iodine.

1 mole of X produces 3 moles of iodine, I2

The iodine liberated can then be titrated with thiosulphate ions, S2O32–, to reduce the iodine

back to iodide.

2Na2S2O3(aq) + I2(aq) → Na2S4O6(aq) + 2NaI(aq)

You are to determine the relative molecular mass of the oxidant X.

(a) Pipette 25.0 cm3 of FA 2 into a conical flask. Use the measuring cylinder provided toadd an excess of iodide ions (approximately 10 cm3 of FA 3), and 10 cm3 of sulphuricacid, FA 4.

Titrate the iodine produced in the conical flask with FA 1. As the titration proceeds thecolour of the iodine in solution will diminish. The end-point is reached when the colourdisappears and the solution becomes colourless.

There is no need to add starch indicator to find the end-point.

Record your results in Table 1.1.



Table 1.1 Titration of Iodine with FA 1

[2] + [6]

Summary

25.0 cm3 of FA 2 produced sufficient iodine to react with ..................... cm3 of FA 1.

Show which results you used to obtain this volume of FA 1 by placing a tick (�) under thereadings in Table 1.1.







(b) Calculate how many moles of sodium thiosulphate, Na2S2O3, were run from theburette during the titration.[Ar: Na, 23.0; S, 32.1; O, 16.0.]

[2]

(c) Calculate how many moles of iodine, I2, react with the sodium thiosulphate run fromthe burette.

[1]

(d) Calculate how many moles of oxidant X were placed in the titration flask at thebeginning of the titration.

[1]

(e) Calculate the concentration, in mol dm–3, of the oxidant X in FA 2.

[1]

(f) Calculate the relative molecular mass, Mr, of the oxidant X.

[2]

[Total: 15]

3


ForExaminer's

Use

© UCLES 2004



2 FA 5 contains two cations and one anion from the following list: (Al3+, NH4+, Ba2+, Ca2+,

Cr3+, Cu2+, Fe2+, Fe3+, Pb2+, Mg2+, Mn2+, Zn2+; CO32–, CrO4

2–, Cl–, Br–, I–, NO3–, NO2

–,SO4

2–, SO32–.).

In all tests, the reagent should be added gradually, with shaking after each addition.Record your observations in the spaces provided.

Your answers should include� details of colour changes and precipitates formed,� the names of gases evolved and details of the test used to identify each one.You should indicate clearly at what stage in a test a change occurs.


Candidates are reminded that definite deductions may be made from tests where thereappears to be no reaction.

4

9701/03/O/N/04

ForExaminer's

Use

© UCLES 2004


(a) To 2 cm depth of FA 5 in a test-tube, add 1 cm depth of aqueous silver nitrate.

Leave the mixture to stand and continuewith tests (b) to (e).

(b) To 2 cm depth of FA 5 in a boiling-tube,add 4 cm depth of aqueous sodiumhydroxide. Stir thoroughly with the glassrod provided.Filter the mixture and retain the filtratefor tests (c), (d) and (e).

Observe the residue in the filter paperafter it has been exposed to the air for afew minutes.

(c) To 1 cm depth of the filtrate from (b) in atest-tube, add 2 cm depth of dilute nitricacid followed by aqueous silver nitrate.

(d) To 1 cm depth of the filtrate from (b) in atest-tube, add 2 cm depth of dilutehydrochloric acid followed by aqueousbarium chloride.



Use the information in the Qualitative Analysis Tables on pages 6 and 7 to identify the ionspresent in FA 5.

The cations present in FA 5 are ........................... and .............................

The anion present in FA 5 is ........................... [1]

Which observations support your choice of these ions?

.................................................................................................................................................

........................................................................................................................................... [1]

What is the identity of the solid formed and dissolved in test (f)? Give a reason.

.................................................................................................................................................

........................................................................................................................................... [1]

[Total: 10]

5


ForExaminer's

Use

© UCLES 2004

Test Observations

(e) Place 1 cm depth of the filtrate from (b)in a boiling-tube and warm the tubegently.Take care as a solution containingsodium hydroxide may ‘bump’ onheating and eject hot corrosivesodium hydroxide.

(f) Observe the mixture left to stand in test (a).

Use a teat pipette to remove the solutionfrom the precipitate formed, then add2 cm depth of distilled water to wash theprecipitate. Allow the precipitate to settleand again use a teat pipette to removethe solution.

Dissolve the solid in 2 cm depth of diluteaqueous nitric acid. You may need tocautiously warm the mixture.Use this solution in the test below.

Add dilute hydrochloric acid to the soliddissolved in nitric acid.







6

9701/03/O/N/04© UCLES 2004

aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion



© UCLES 2004


3 Tests for gases

7

9701/03/O/N/04

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2




BLANK PAGE


8

9701/03/O/N/04




SP (SJF3515) S81618/4© UCLES 2005 [Turn over



CHEMISTRY 9701/03


1 hour 15 minutesCandidates answer on the Question Paper.Additional Materials: as listed in the Instructions to Supervisors.



Answer all questions.The number of marks is given in brackets [ ] at the end of each question or part question.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualitative Analysis Notes are printed on pages 6 and 7.



1

2

TOTAL

SESSION

LABORATORY



© UCLES 2005

2

9701/03/O/N/05

ForExaminer's

Use

1 FA 1 is an aqueous solution containing 38.10 g dm–3 of borax crystals. Borax is disodium tetraborate-x-water, Na2B4O7.xH2O.FA 2 is 1.00 mol dm–3 HCl.

You are required to find the number of moles of water of crystallisation, x, in the boraxcrystals.Disodium tetraborate reacts with hydrochloric acid according to the equation below.

Na2B4O7(aq) + 2HCl (aq) + 5H2O(l) → 2NaCl (aq) + 4H3BO3(aq)

(a) Use a burette to measure between 44.50 cm3 and 45.50 cm3 of FA 2 into the 250cm3

volumetric (graduated) flask labelled FA 3.Record your burette readings in Table 1.1.

Table 1.1 Dilution of FA 2

Fill the flask to the 250 cm3 mark with distilled or deionised water and mix the contentsthoroughly by shaking. This solution is FA 3.

Fill the second burette with the diluted hydrochloric acid, FA 3.

(b) Pipette 25.0 cm3 of FA 1 into a conical flask and add a few drops of the indicatorprovided. Titrate the contents of the conical flask with FA 3 until the appropriate colourchange is observed at the end-point.

Repeat the titration as many times as you think necessary to obtain accurateresults. Make certain that the recorded results show the precision of your practical work.


The indicator used was ...................................................................................................

Summary


Show which results you used to obtain this volume of FA 3 by placing a tick (✓) under thereadings in Table 1.2.

[6]










(c) Calculate the concentration, in mol dm–3, of hydrochloric acid in the diluted solution FA 3.

[1]

(d) Calculate how many moles of hydrochloric acid were run from the burette into theconical flask during the titration of FA 1 with FA 3.

[1]

(e) Calculate the concentration, in mol dm–3, of the disodium tetraborate in FA 1.

Na2B4O7(aq) + 2HCl (aq) + 5H2O(l) → 2NaCl(aq) + 4H3BO3(aq)

[2]

(f) Calculate the concentration, in g dm–3, of disodium tetraborate, Na2B4O7, in FA 1.[Ar: Na, 23.0; B, 10.8; O, 16.0.]

[2]

(g) FA 1 contains 38.10 g dm–3 of borax crystals, Na2B4O7.xH2O. Use this information andyour answer to (f) to calculate the mass of water present in the dissolved crystals.

[1]

(h) Calculate the number of moles of water present in 38.10 g of borax crystals.

Use this answer and the answer to (e) to calculate the value of x in Na2B4O7.xH2O.

[2][Total:15]

3


ForExaminer's

Use

© UCLES 2005



2 FA 4 contains one cation from those listed on page 6.FA 4 also contains one anion but this is not an ion listed on page 7.

In all tests, the reagent should be added gradually until no further change is observed, withshaking after each addition.Record your observations in the spaces provided.Your answers should include• details of colour changes and precipitates formed,• the names of gases evolved and details of the test used to identify each one.You should indicate clearly at what stage in a test a change occurs.


4

9701/03/O/N/05

ForExaminer's

Use

© UCLES 2005



(a) Transfer two thirds of the solid FA 4 to aboiling-tube and add about 7 cm depth ofdilute nitric acid.Cautiously warm the tube until theorange colour of the solid is no longervisible.

Filter the mixture and retain filtrate forfurther tests.Wash the residue with water and retainresidue for further tests.

(b) Transfer the remaining solid FA 4 to ahard glass test-tube and heat strongly.

Identify, with a suitable test, the gasevolved.

Tests on the filtrate

(c) To 1 cm depth of the filtrate from (a) in atest-tube, add aqueous sodiumhydroxide until there is no furtherchange.

(d) To 1 cm depth of the filtrate from (a) in atest-tube, add aqueous ammonia untilthere is no further change.

By performing the tests below, you should be able to identify the cation and to draw afurther conclusion as to the nature of FA 4.



(e) To 1 cm depth of the filtrate from (a) in atest-tube, add aqueous potassium iodide.

Tests on residue

(f) Cautiously place 1 cm depth ofconcentrated hydrochloric acid into aboiling-tube and add an equal volume ofwater.

Add to the tube some of the residue from(a) and warm gently. Identify, with asuitable test, the gas evolved.

Immediately the gas is identified rinsethe contents of the tube into the sink.

5


ForExaminer's

Use

© UCLES 2005

Test Observations

Use the information in the Qualitative Analysis Tables on pages 6 and 7 to identify the cationpresent in FA 4.

The cation present in FA 4 is ................................................................................................

Give two pieces of evidence that support your choice of this ion.

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [2]

FA 4 behaves as ....................................................................................................................

Give one piece of evidence that supports this behaviour.

.................................................................................................................................................

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [2]

[Total: 10]







6

9701/03/O/N/05© UCLES 2005

aluminium,Al 3+(aq)

ammonium,NH4

+(aq)

barium,Ba2+(aq)

calcium,Ca2+(aq)


zinc,Zn2+(aq)

copper(II),Cu2+(aq)

iron(II),Fe2+(aq)

iron(III),Fe3+(aq)

lead(II),Pb2+(aq)

magnesium,Mg2+(aq)


reaction with

NaOH(aq) NH3(aq)




















no ppt.

no ppt.



ion



© UCLES 2005


3 Tests for gases

7

9701/03/O/N/05

carbonate,CO3

2–

chromate(VI),CrO4

2–(aq)

chloride,Cl–(aq)

bromide,Br–(aq)

iodide,I–(aq)

nitrate,NO3

–(aq)

nitrite,NO2

–(aq)

sulphate,SO4

2–(aq)

sulphite,SO3

2–(aq)

ion reaction

















ammonia, NH3

carbon dioxide, CO2

chlorine, Cl 2

hydrogen, H2

oxygen, O2




BLANK PAGE

8

9701/03/O/N/05






SP (NF) T20258/3© UCLES 2006 [Turn over



CHEMISTRY 9701/03




Write your Centre number, candidate number and name, including practical session and laboratory where appropriate, in the spaces provided.Write in dark blue or black pen.You may use a soft pencil for any diagrams, graphs or rough working.Do not use staples, paper clips, highlighters, glue or correction fluid.

Answer all questions.You are advised to show all working in calculations.Use of a Data Booklet is unnecessary.Qualitative Analysis Notes are provided on pages 7 and 8.

At the end of the examination, fasten your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.



1

2

Total

Session

Laboratory



2

9701/03/O/N/06

ForExaminer’s

Use

© UCLES 2006

1 FA 1 is an aqueous solution of hydrochloric acid, HCl. FA 2 is aqueous potassium iodate(V) containing 4.93 g dm–3 of KIO3. FA 3 is aqueous potassium iodide, KI. FA 4 is aqueous sodium thiosulphate, Na2S2O3.

In the presence of acid, iodate(V) ions react with iodide ions to form iodine and water.

IO3–(aq) + 5I–(aq) + 6H+(aq) 3I2(aq) + 3H2O(l)

If sodium thiosulphate is present in the reaction mixture the iodine formed is immediately reduced back to iodide and the solution remains colourless.

Iodate(V) ions can therefore be titrated against acid in the presence of an excess of iodide and thiosulphate ions.

You are to use this method to determine the concentration of the hydrochloric acid, FA 1.

(a) Dilution of FA 1 Using a burette, run between 34.00 cm3 and 35.00 cm3 of FA 1 into the 250 cm3

graduated flask, labelled FA 5. Record the burette readings in Table 1.1.

Table 1.1 Dilution of FA 1



volume of FA 1 run into the flask / cm3

Make the solution up to 250 cm3 with distilled water and mix thoroughly. Fill a second burette with this diluted acid, FA 5.

(b) Titration of IO3– with H+ in FA 5

Pipette 25.0 cm3 of FA 2 into a conical flask and use a measuring cylinder to add to the flask 10 cm3 of FA 3 and 25 cm3 of FA 4.

Add five drops of bromophenol blue indicator and titrate with FA 5 until the end-point is reached.

The colour of bromophenol blue changes to yellow at the end-point.

Record your titration results in Table 1.2.

Repeat the titration as many times as you think necessary to obtain accurate results. Make certain that the recorded results show the precision of your practical work.





[8]

Summary

25.0 cm3 of FA 2 reacted with ....................... cm3 of FA 5.

Show which results you used to obtain this volume of FA 5 by placing a tick (✓) under the readings in Table 1.2.



3


ForExaminer’s

Use

© UCLES 2006


(c) Calculate how many moles of potassium iodate(V), KIO3, were pipetted into the conical flask.

[Ar: K, 39.1; I, 127.0; O, 16.0]

[2]

(d) Calculate how many moles of hydrogen ions, H+, reacted with the iodate(V) ions in the flask during the titration.

IO3–(aq) + 5I–(aq) + 6H+(aq) 3I2(aq) + 3H2O(l)

[1]

(e) Calculate the concentration, in mol dm–3, of hydrogen ions in FA 5.

[1]

(f) Calculate the concentration, in g dm–3, of hydrochloric acid in FA 1. [Ar: H, 1.0; Cl, 35.5]

[3]

[Total: 15]



4

9701/03/O/N/06

ForExaminer’s

Use

© UCLES 2006

2 FA 6 is a mixture of two solids provided in a stoppered boiling tube. One of the solids, FA 7 is soluble in water; the other, FA 8 is insoluble in water. Each solid contains one cation and one anion from the ions listed on pages 7 and 8.

In all tests, the reagent should be added gradually with shaking after each addition. Record your observations in the spaces provided. Your answers should include • details of colour changes, precipitates formed and the solubility of any precipitate

when an excess of the reagent is added, • details of the test used to identify any gases given off in the reaction. You should indicate clearly at what stage in a test a change occurs.

Marks are not given for chemical equations. No additional or confirmatory tests for ions present should be attempted.

Candidates are reminded that definite deductions may be made from tests where there appears to be no reaction.

test observations [3]

(a) Add water to the boiling-tube labelled FA 6 until it is about half-full. Stopper and shake the tube for 1 minute.

Filter the mixture and retain both filtrate and residue for further tests.

Tests on the filtrate which contains FA 7

(b) To 1 cm depth of the filtrate from (a), in a boiling-tube, add 2 cm depth of aqueous sodium hydroxide.

Gently warm the solution.Take care as a solution containing sodium hydroxide may ‘bump’ on heating and eject hot corrosive sodium hydroxide.

(c) To 1 cm depth of the filtrate from (a), in a boiling-tube, add 1 cm depth of aqueous lead(II) nitrate; then

heat the mixture to boiling point; then

cool the tube by standing in a beaker of cold water.



5


ForExaminer’s

Use

© UCLES 2006

test observations

(d) To 1 cm depth of the filtrate from (a), in a test-tube, add 5 drops of aqueous silver nitrate; then

add 5 cm depth of dilute aqueous ammonia.

Use the information in the Qualitative Analysis Notes on pages 7 and 8 to identify the ions present in FA 7.

The cation present in FA 7 is .................................

Which observations indicate the cation you have selected?

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [1]

The anion present in FA 7 is .................................

Which observations indicate the anion you have selected?

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [1]



6

9701/03/O/N/06

ForExaminer’s

Use

© UCLES 2006

Tests on the residue which contains FA 8

test observations [3]

(e) Transfer the residue to a boiling-tube and add 4 cm depth of dilute hydrochloric acid.Filter the mixture and retain the filtrate.

(f) To 1 cm depth of the filtrate from (e) in a test-tube add, a little at a time, 5 cm depth of aqueous sodium hydroxide.

(g) To 1 cm depth of the filtrate from (e) in a test-tube add, a little at a time, 5 cm depth of dilute aqueous ammonia.

Use the information in the Qualitative Analysis Notes on pages 7 and 8 to identify the ions present in FA 8.

The cation present in FA 8 is .................................

Which observations indicate the cation you have selected?

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [1]

The anion present in FA 8 is .................................

Which observations indicate the anion you have selected?

.................................................................................................................................................

.................................................................................................................................................

............................................................................................................................................ [1]

[Total: 10]



7

9701/03/O/N/06© UCLES 2006 [Turn over




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH4


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






8

9701/03/O/N/06© UCLES 2006


ion reaction

carbonate,CO3


chromate(VI),CrO4

2–(aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO3


nitrite,NO2

–(aq)NH3 liberated on heating with OH–(aq) and Al foil;NO liberated by dilute acids(colourless NO (pale) brown NO2 in air)

sulphate,SO4


sulphite,SO3


3 Tests for gases









University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.



This document consists of 12 printed pages and 1 Insert.

SP (SM/KS) T47239/2© UCLES 2007 [Turn over







*3318230628*

CHEMISTRY 9701/31

Paper 31 Practical Test October/November 2007

2 hours




1

2

Total

Session

Laboratory



2

9701/31/O/N/07© UCLES 2007


You are provided with the following reagents.

FA 1 containing 37.0 g dm–3 of hydrated sodium thiosulphate, Na2S2O3.5H2O FA 2 2.0 mol dm–3 hydrochloric acid, HCl distilled water

Aqueous thiosulphate ions, S2O32–, decompose in the presence of hydrogen ions, H+.

S2O32–(aq) + 2H+(aq) → S(s) + SO2(g) + H2O(l)

The rate of reaction can be followed by observing the formation of a fixed amount of sulphur as a fine suspension of solid particles in the solution.

The rate of decomposition at a fixed temperature is affected by

• the concentration of thiosulphate ions, [S2O32–];

• the concentration of hydrogen ions, [H+].

In a series of experiments where the concentration of a reagent is changed

• 1/time can be used as a measure of rate, • the volume of the reagent used can be taken as a measure of its concentration,

providing the total volume of the mixture is kept constant in each experiment.

The order of reaction with respect to thiosulphate ions can be obtained by plotting a graph of log rate against log [S2O3

2–].

order of reaction = gradient of straight line

log [S2O32–]

log rate

ForExaminer’s

Use



3

9701/31/O/N/07 [Turn over© UCLES 2007

(a) Method

Experiment 1

• Fill the burette labelled FA 1 with FA 1. • Run 50.00 cm3 of FA 1 from the burette into a 250 cm3 beaker. • Measure 5 cm3 of FA 2 in a measuring cylinder. • Tip the acid FA 2 from the measuring cylinder into the beaker and immediately

start a stop-clock or note the start time on a clock with a second hand. • Swirl the beaker to mix the reagents and place the beaker over the printing on the

insert provided. • Observe the printing by looking down through the solution in the beaker. • Stop the clock or note the time when the printing is just no longer visible. • Record the time taken to the nearest second.

The time taken is ................. s.

Experiment 2

• Empty and rinse the beaker used in experiment 1. Carefully dry the beaker with a paper towel.

• Refill the burette labelled FA 1 with FA 1. • Fill the second burette, labelled water, with distilled water. • Run 10.00 cm3 of FA 1 and 40.00 cm3 of distilled water from the burettes into the

250 cm3 beaker. • Measure 5 cm3 of FA 2 in a measuring cylinder. • Tip the acid FA 2 into the beaker, start the clock or note the time, mix the reagents

and place over the printing as in experiment 1. • Stop the clock or note the time when the printing is just no longer visible. • Record the time taken to the nearest second.

The time taken is ................. s.[2]

ForExaminer’s

Use



4

9701/31/O/N/07

ForExaminer’s

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© UCLES 2007

(b) In experiment 1 you will have obtained the time taken for a ‘fast’ reaction and inexperiment 2 the time taken for a ‘slow’ reaction.

You are to repeat the experiment with further mixtures in which only the concentration of thiosulphate ions is varied.

In selecting the mixtures to be used you should consider • how many mixtures need to be used, • what concentrations of thiosulphate ion should be used, • what range these concentrations should cover, • that only the concentration of thiosulphate ion must change.

Remember – you already have reaction times for two mixtures with different concentrations of thiosulphate ion.

In the space below prepare to record, in an appropriate form, the results of the experiments you will perform and the results of experiments 1 and 2.

Your recorded results should include calculated values to enable you to plot

log (1/time) against log (volume of FA 1).

Carry out the additional experiments and record your results.

[11]

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(c) Use the grid below to plot a graph of log (1/time) against log (volume of FA 1). Draw an appropriate straight line through the points plotted.

[4]



6

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ForExaminer’s

Use

© UCLES 2007

(d) Draw construction lines on your graph and obtain data from them to enable you to calculate the gradient of the graph.

Calculate the gradient of the line drawn, which is the order of reaction with respect to thiosulphate ions.

The reaction is ................................ order with respect to thiosulphate ions, S2O32–. [3]

(e) The moment at which the printing is just obscured can be difficult to judge and will vary from person to person.

Explain why this uncertainty for experiment 1 in section (a) will be less than the uncertaintyfor experiment 2 in section (a).

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Estimate a value (± seconds) for the uncertainty in each of experiments 1 and 2 and express this uncertainty as a percentage of the time for the reaction.


reaction time / s

uncertainty / s ± ±

percentage uncertainty

[3]



7


ForExaminer’s

Use

© UCLES 2007

(f) The experimental method can be modified to enable the rate of reaction with respect to hydrogen ions, H+, to be investigated.

You will perform two further experiments using the method for experiment 2 in section (a). You will keep the concentration of thiosulphate ions constant and vary the concentration of hydrogen ions.

First copy the reaction time from your results to experiment 2 in section (a) into the table below. Then complete the table below to show the volumes of FA 1, FA 2, and distilled water you will use in these two further experiments.

Carry out each experiment as before and record the time taken in each case.

volume of FA 1/ cm3

volume of FA 2/ cm3

volume water/ cm3

reaction time/ s

experiment 2in section (a) 10.00 5 40.00

experiment i

experiment ii

[1]

(g) Use the experimental results from the three experiments to draw a conclusion as to how the rate of reaction is affected by changing the concentration of hydrogen ions.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total: 25]



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ForExaminer’s

Use

© UCLES 2007

2 The four solutions FA 3, FA 4, FA 5 and FA 6 each contain one of the following anions.

nitrate, NO3–

nitrite, NO2–

sulphate, SO42–

sulphite, SO32–

(a) Use information from the Qualitative Analysis Notes on page 12 to answer the following questions.

What single reagent could you use to identify the solution containing the nitrite ion?

..........................................................................................................................................

What reagents could you use to identify the sulphate and sulphite ions?

................................................................. and .................................................................[1]

(b) Use the reagents selected in (a) to test each of the four solutions.

Record in the space below, the reagents used and the observations made.

From your observations identify the solutions containing nitrite, sulphate and sulphite ions.

Solution ................ contains the nitrite ion.

supporting evidence ........................................................................................................

Solution ................ contains the sulphate ion.


Solution ................ contains the sulphite ion.

supporting evidence ........................................................................................................[7]



9


ForExaminer’s

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© UCLES 2007

(c) You are to perform the tests given in the table below with each of the solutions FA 3, FA 4,FA 5 and FA 6 to identify three of the cations present. One of these cations is theBa2+ ion.


Where gases are released they should be identified by a test, described in the appropriate place in the table.


Marks are not given for chemical equations. No additional tests should be attempted.

testobservations

FA 3 FA 4 FA 5 FA 6

(i) To 1 cm depth of solution in a boiling-tube, add aqueous sodium hydroxide a little at a time until there is no further change.

If no precipitate forms, carefully warm the solution.

CARE - heated solutions containing sodium hydroxide can be ejected from the boiling-tube.

(ii) To 1 cm depth of solution in a test-tube, add aqueous ammonia a little at a time until there is no further change.

(iii) To 1 cm depth of solution in a test-tube add 1 cm depth of dilute sulphuric acid.

(iv) To 1 cm depth ofsolution in a test-tubeadd 1 cm depth of aqueous sodium sulphite.

If a precipitate forms, add 2 cm depth of dilute hydrochloric acid.

[3]



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ForExaminer’s

Use

© UCLES 2007

(d) From your observations in (c) you should be able to identify the cation present in three of the solutions.

Solution ................ contains the ................ ion.


..........................................................................................................................................



..........................................................................................................................................



..........................................................................................................................................[3]

(e) Do not carry out this test.

What other reagent could you use to confirm the presence of Ba2+ in one of the solutions?

......................................................................................................................................[1]

[Total: 15]



11

9701/31/O/N/07© UCLES 2007




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/31/O/N/07© UCLES 2007


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)

gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid)

sulphite,SO2–

3 (aq)


3 Tests for gases













SP (SM/KS) T47240/1© UCLES 2007 [Turn over







*7735436310*

CHEMISTRY 9701/32


2 hours




1

2

Total

Session

Laboratory



2

9701/32/O/N/07© UCLES 2007



FB 1, 1 mol dm–3 sulphuric acid, H2SO4 FB 2, 0.1 mol dm–3 potassium iodide, KI FB 3, 0.1 mol dm–3 sodium thiosulphate, Na2S2O3 FB 4, 0.1 mol dm–3 hydrogen peroxide, H2O2 starch solution distilled water

In the presence of an acid, iodide ions are oxidised by hydrogen peroxide to iodine.

H2O2(aq) + 2H+(aq) + 2I–(aq) → 2H2O(l) + I2(aq)

The rate of reaction can be followed by timing the formation of a fixed amount of iodine in the solution.

If sodium thiosulphate is present in the reaction mixture it reacts with the iodine formed and the solution remains colourless.

I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O6

2–(aq)

When all of the sodium thiosulphate present has reacted, iodine, I2, will appear in the solution producing an immediate blue colour with starch indicator.

In a series of experiments where the concentration of a reagent is changed

• 1/time can be used as a measure of rate, • the volume of the reagent used can be taken as a measure of its concentration

providing the total volume of the mixture is kept constant in each experiment.

The order of reaction with respect to hydrogen peroxide can be obtained by plotting a graph of log rate against log [H2O2].

order of reaction = gradient of straight line

log [H2O2]

log rate

ForExaminer’s

Use



3


(a) Method

Experiment 1

• Fill the burette labelled FB 3 with FB 3 and the burette labelled FB 4 with FB 4. • Use the measuring cylinder labelled A to put the following solutions into a 250 cm3

conical flask: 20 cm3 of FB 2, potassium iodide, 20 cm3 of distilled water. • Add to the flask from the burette 1.00 cm3 of FB 3, sodium thiosulphate. • Add six drops of starch indicator to the mixture in the flask. • Run 20.00 cm3 of FB 4, hydrogen peroxide, from the second burette into a 100 cm3

beaker. • Use the measuring cylinder labelled B to add 20 cm3 of FB 1, sulphuric acid, to the

hydrogen peroxide in the beaker. • Tip the contents of the beaker into the conical flask and immediately start a

stop-clock or note the start time on a clock with a second hand. • Swirl the flask to mix the reagents. • Observe the solution and stop the clock or note the time when the solution suddenly

turns blue. • Record the time taken to the nearest second.

The time taken is ................. s.

Experiment 2

• Empty, thoroughly rinse and drain the conical flask used in experiment 1. • Use the measuring cylinder labelled A to put the following solutions into the

250 cm3 conical flask: 20 cm3 of FB 2, potassium iodide, 35 cm3 of distilled water. • Add to the flask from the burette 1.00 cm3 of FB 3, sodium thiosulphate. • Add six drops of starch indicator to the mixture in the flask. • Run 5.00 cm3 of FB 4, hydrogen peroxide, from the second burette into a 100 cm3

beaker. • Use the measuring cylinder labelled B to add 20 cm3 of FB 1, sulphuric acid, to the

hydrogen peroxide in the beaker. • Tip the contents of the beaker into the conical flask and immediately start a

stop-clock or note the start time on a clock with a second hand. • Swirl the flask to mix the reagents. • Observe the solution and again stop the clock or note the time when the solution

suddenly turns blue. • Record the time taken to the nearest second.

The time taken is ................. s.[2]

ForExaminer’s

Use



4

9701/32/O/N/07

ForExaminer’s

Use

© UCLES 2007

(b) In experiment 1 you will have obtained the time taken for a ‘fast’ reaction and inexperiment 2 the time taken for a ‘slow’ reaction.

You are to repeat the experiment with further mixtures in which only the concentration of hydrogen peroxide is varied.

In selecting the mixtures to be used you should consider • how many mixtures need to be used, • what concentrations of hydrogen peroxide should be used, • what range these concentrations should cover, • that only the concentration of hydrogen peroxide must change.

Remember – you already have reaction times for two mixtures with different concentrations of hydrogen peroxide.

In the space below prepare to record, in an appropriate form, the results of the experiments you will perform and the results of experiments 1 and 2.

Your recorded results should include calculated values to enable you to plot

log (1/time) against log (volume of FB 4).

Carry out the additional experiments and record your results.

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(c) Use the grid below to plot a graph of log (1/time) against log (volume of FB 4). Draw an appropriate straight line through the points plotted.

[4]



6

9701/32/O/N/07

ForExaminer’s

Use

© UCLES 2007

(d) Draw construction lines on your graph and obtain data from them to enable you to calculate the gradient of the graph.

Calculate the gradient of the line drawn, which is the order of reaction with respect to hydrogen peroxide.

The reaction is ................................ order with respect to hydrogen peroxide, H2O2. [3]

(e) In experiment 1 burettes and measuring cylinders were used to measure volume.

A burette is graduated to 0.10 cm3 and is usually read to the nearest 0.05 cm3. A 25 cm3 measuring cylinder is graduated to 0.5 cm3.

Estimate the error when measuring a volume of 20 cm3 in a 25 cm3 measuring cylinder.

The error is ± ……………………… cm3.

Use this answer and the information above to calculate the percentage error for each volume measurement made in experiment 1. Complete the table below.

solutionapparatus

usedvolume/ cm3

error/ cm3 % error

FB 1, FB 2,distilled water

25 cm3 measuringcylinder

20

FB 3 burette 1.00

FB 4 burette 20.00

Identify the most significant source of error in this experiment.

..........................................................................................................................................

......................................................................................................................................[3]



7


ForExaminer’s

Use

© UCLES 2007

(f) The experimental method can be modified to enable the rate of reaction with respect to iodide ions, I–, to be investigated.

You will perform two further experiments using the method for experiment 1 in section (a). You will keep the concentration of hydrogen peroxide constant and reduce the concentration of iodide ions.

First copy your reaction time from experiment 1 in section (a) into the table below. Then complete the table below to show the volumes of FB 2 and distilled water you will use in these two further experiments.

Carry out each experiment as before and record the time taken in each case.

volume FB 1(H2SO4)

/ cm3

volume FB 2(KI)

/ cm3

volumewater

/ cm3

volume FB 3(Na2S2O3)

/ cm3

volume FB 4(H2O2)

/ cm3

reactiontime

/ s

experiment 1in section (a) 20 20 20 1.00 20.00

experiment i 20 1.00 20.00

experiment ii 20 1.00 20.00

[1]

(g) Use the experimental results from the three experiments to draw a conclusion as to how the rate of reaction is affected by changing the concentration of iodide ions.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

[Total: 25]



8

9701/32/O/N/07

ForExaminer’s

Use

© UCLES 2007

2 The three solutions FB 5, FB 6, and FB 7 each contain one of the following.

copper(II) chloride, CuCl 2 chromium(III) chloride, CrCl 3 nickel(II) sulphate, NiSO4

(a) Use information from the Qualitative Analysis Notes on page 12 to select a pair of reagents that you could use to determine which solution contains the sulphate ion.

Carry out the tests and record, in the space below, the reagents used and the observations made.

From these tests, solution FB ................. contains the sulphate ion.[3]

(b) The solutions containing copper(II) and chromium(III) ions can be distinguished from one another by adding either aqueous sodium hydroxide or aqueous ammonia.Nickel(II) ions behave in a similar way to copper(II) ions with these reagents.

Add NaOH(aq) and NH3(aq) separately to each of the solutions FB 5, FB 6 and FB 7.

Record your observations in the space below.



9


ForExaminer’s

Use

© UCLES 2007

From your observations in (a) and (b) identify the solutions containing copper(II) ions and chromium(III) ions.

Solution ................ contains Cu2+.


..........................................................................................................................................

Solution ................ contains Cr3+.


..........................................................................................................................................[5]

(c) You are to perform the tests given in the table below on the solid FB 8 and to comment on the type of compound present in FB 8.


Where gases are released they should be identified by a test, described in the appropriate place in your table.



No additional tests should be attempted.

test observations with FB 8

(i) To 2 cm depth of distilled water in a boiling-tube, add 1 spatula measure of FB 8.

Warm to dissolve the solid and immediately add a 1 cm length of magnesium ribbon.

(ii) To 1 cm depth of aqueous sodium hydroxide in a test-tube,add 1 spatula measure of FB 8.

Stir the mixture, then add 2 cm depth of dilute hydrochloric acid.

Stir the mixture, then add 3 cm depth of aqueous sodium hydroxide.



10

9701/32/O/N/07

ForExaminer’s

Use

© UCLES 2007

test observations with FB 8

(iii) To 1 cm depth of ethanol in a boiling-tube, add 2 spatula measures of FB 8 and a few drops of concentrated sulphuric acid (CARE: corrosive).

Heat the contents of the tube for 1-2 minutes, using the apparatus provided for heating a flammable liquid (CARE).

Pour the contents of the tube into a 100 cm3 beaker full of water.

From your observations, draw conclusions about the type of compound present inFB 8.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[7]

[Total: 15]



11

9701/32/O/N/07© UCLES 2007




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/O/N/07© UCLES 2007


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)


sulphite,SO2–

3 (aq)


3 Tests for gases













SP (SM) T69055/1© UCLES 2008 [Turn over







*9494840911*

CHEMISTRY 9701/31

Paper 31 Advanced Practical Skills October/November 2008

2 hours




1

2

3

Total

Session

Laboratory



2

9701/31/O/N/08© UCLES 2008

ForExaminer’s

Use

1 FA 1 contains the monoprotic (monobasic) acid RCO2H. You are to determine the relative molecular mass, Mr, of the acid and deduce its molecular formula.

You are provided with the following.

FA 1, the aqueous acid, containing 38.68 g dm–3 RCO2H FA 2, aqueous sodium hydroxide containing 3.40 g dm–3 NaOH Phenolphthalein indicator.

(a) Dilution of FA 1

By using a burette measure between 38.00 cm3 and 39.00 cm3 of FA 1 into the 250 cm3 graduated (volumetric) flask labelled FA 3.



Titration

Fill a second burette with FA 3, the diluted solution containing RCO2H.

Pipette 25.0 cm3 of FA 2 into the conical flask and add 2–3 drops of phenolphthalein indicator.

Titrate the sodium hydroxide in the flask with FA 3 until the solution just turns colourless.



[6]

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ForExaminer’s

Use

(b) From your titration results obtain a volume of FA 3 to be used in your calculations. Show clearly how you obtained this volume.

[1]

Calculations


(c) Calculate how many moles of NaOH have been pipetted into the conical flask. [Ar: H, 1.0; O, 16.0; Na, 23.0]

…………………. mol of NaOH were pipetted into the conical flask.

Use your titre volume in (b) and the answer above to calculate how many moles of RCO2H are contained in 250 cm3 of the diluted acid FA 3.

250 cm3 of FA 3 contains …………………. mol of RCO2H.

Use this answer to calculate the concentration, in mol dm–3, of the undiluted acid in FA 1.

The concentration of RCO2H in FA 1 is …………………. mol dm–3.

Use this answer to calculate, correct to 3 significant figures, the relative molecular mass, Mr, of RCO2H.

The relative molecular mass, Mr , of RCO2H is ……………………. .

Use this answer to deduce the formula of the acid RCO2H.

The formula of RCO2H is ……………………. .[5]

[Total: 12]

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9701/31/O/N/08© UCLES 2008

ForExaminer’s

Use

2 You are required to find the percentage by mass of water of crystallisation in FA 4, hydrated magnesium sulphate, MgSO4.xH2O.

The water contained in the crystals can be removed by heating the crystals.

Method

(a) Follow the instructions below to determine the mass of water driven off when heating magnesium sulphate crystals.

• Weigh the empty hard glass boiling-tube. • Tip the contents of the tube labelled FA 4 into the boiling-tube. • Reweigh the boiling-tube and FA 4. • Hold the boiling-tube in the holder provided and heat gently at first, then

strongly for several minutes. • Leave the boiling-tube to cool on a heat-proof mat. • Carry on with other parts of the paper, e.g. question 3, while the boiling-tube

cools. • When cool weigh the boiling-tube and its contents. • Continue the heating, cooling and weighing until you are satisfied that all of the

water of crystallisation has been driven from the crystals.

In an appropriate form record below

• all measurements of mass, • the final mass of the residue and the mass of water driven off.

Results

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Calculations

(b) Calculate the percentage by mass of water of crystallisation in the crystals.

Hydrated magnesium sulphate crystals contain …………… % of water by mass.[1]

(c) Use the relative molecular mass information provided to complete the table below. [Mr: MgSO4, 120.4; H2O, 18.0]

possible value of x in MgSO4.xH2O

% water by mass

1 13.0

2 23.0

3

4 37.4

5 42.8

6 47.3

7 51.1

8 54.5

9

10 59.9

Use your answer in (b) and the information in the table to find the experimental value of x in the formula MgSO4.xH2O.

…………….. is the value of x in MgSO4.xH2O.[2]

(d) A student is instructed to repeat the whole experiment to ensure reliability of results. Explain how repeating the experiment would lead to greater reliability in the experimental

results.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]



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ForExaminer’s

Use

(e) On a balance weighing to 1 decimal place assume the maximum error is ±0.1 g. What mass would have to be weighed out on this balance to result in an error of

0.04%?

The mass is ………………………. g.[1]

[Total: 12]

3 FA 5 is a solid metal oxide. FA 6 and FA 7 are aqueous solutions.

You will carry out specified tests to deduce

• the chemical properties of FA 5 and FA 7, • the identities of the anion and cation present in FA 6.


• colour changes seen • the formation of any precipitate • the solubility of such precipitates in an excess of the reagent added.





(a) Pour 1 cm depth of FA 7 into a boiling-tube, stand the tube in a test-tube rack and, using a spatula, add a very small amount of the solid FA 5.

A vigorous reaction will be observed.

The gas evolved is one of carbon dioxide, hydrogen or oxygen.

By considering the density of each gas compared to that of air, you are to decide which of these three gases you should test for first. Explain your answer.

[Ar: C, 12.0; H, 1.0; O, 16.0] [1 mol of any gas occupies approximately 24 dm3 at room temperature and pressure.] [24 dm3 of air at room temperature and pressure has a mass of approximately 25.6 g.]

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................



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ForExaminer’s

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Add a further 1 cm depth of FA 7 to the boiling-tube. Test and identify the gas given off. Record in a suitable form the test or tests performed and the observation made for any

test carried out.

Deduce the identity of the gas evolved.

The gas evolved is ……………………………… .[4]

(b) Place 1 cm depth of 10% potassium iodide solution, KI, in a test-tube and add a very small amount of FA 5. Observe, then add a few drops of starch solution.

Record the tests used and all of your observations in an appropriate form below.

[2]

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(c) Conclusions about the chemical properties of FA 5

In test (a) FA 5 remained unchanged at the end of the reaction.

FA 5 was acting as ………………………………… in this reaction.

In test (b) FA 5 was acting as ………………………………… .

Where in the Periodic Table might you find the metallic element contained in FA 5?

..........................................................................................................................................[2]

(d) To 1 cm depth of FA 6 in a boiling-tube add an equal volume of FA 7. Mix thoroughly by gently shaking the tube.

Using aqueous sodium hydroxide and aqueous ammonia you are to identify the cation present in FA 6, and the cation present in the mixture of FA 6 and FA 7.

Record all of your observations in the table below.

observations

test FA 6 mixture of FA 6 and FA 7

To 1 cm depth of solution in a test-tube add, drop by drop, 1 cm depth of aqueous sodium hydroxide.

Stir the mixture, then adda further 1 cm depth ofaqueous sodium hydroxide.

To 1 cm depth of solution in a test-tube add, drop by drop, 1 cm depth of aqueous ammonia.

Stir the mixture, then add a further 1 cm depth of aqueous ammonia.

Conclusions

The cation present in FA 6 is ……………………….......... .

The cation present in the mixture of FA 6 and FA 7 is ……………………….......... .

When FA 6 and FA 7 reacted together, FA 7 was acting as ……………………….......... .[5]

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(e) Solution FA 6 was prepared using a bottle of solid whose label was partly missing. The solid is believed to contain the sulphate ion, SO4

2–, but may contain the sulphite ion, SO3

2–.

By selecting appropriate reagents from those listed on page 12 of the qualitative analysis notes show that sulphate ions, SO4

2–, are present.

Record your tests, observations and conclusions in an appropriate form below.

[3]

[Total: 16]



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BLANK PAGE



11

9701/31/O/N/08© UCLES 2008




ion reaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/31/O/N/08© UCLES 2008


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)


sulphite,SO2–

3 (aq)


3 Tests for gases







sulphur dioxide, SO2 turns aqueous potassium dichromate(VI) (aq) from orange to green






SP (SC/KS) T56858/2© UCLES 2008 [Turn over







*5473604620*

CHEMISTRY 9701/32


2 hours




1

2

3

Total

Session

Laboratory



2

9701/32/O/N/08© UCLES 2008

1 You are required to find the concentration in mol dm–3 of sodium thiosulphate, Na2S2O3, in solution FB 1.

FB 1 contains sodium thiosulphate. FB 2 is potassium manganate(VII) containing 28.44 g dm–3 KMnO4. FB 3 is 1.0 mol dm–3 sulphuric acid, H2SO4. FB 4 is 10% potassium iodide containing 100 g dm–3 KI. You are also provided with starch indicator.

Dilution of FA 2

(a) By using a burette measure between 41.00 cm3 and 42.00 cm3 of FB 2 into the 250 cm3 graduated (volumetric) flask labelled FB 5.



Titration

Fill a second burette with FB 1, the solution containing sodium thiosulphate.

Use a measuring cylinder to transfer 10 cm3 of FB 3 and 10 cm3 of FB 4 into a conical flask. Pipette 25.0 cm3 of FB 5 into the conical flask containing the mixture of FB 3 and FB 4. The potassium manganate(VII) oxidises potassium iodide to iodine, I2.

Titrate the liberated iodine with FB 1 as follows. Run the solution from the burette into the conical flask until the initial red/brown colour of the iodine becomes pale yellow. Then add 1 cm3 of the starch indicator and continue to add FB 1 drop by drop until the blue/black colour of the starch/iodine complex disappears, leaving a colourless solution. This is the end-point of the titration.



[6]

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The volume of FB 5 is …………….. cm3. [1]

Calculations


(c) Calculate how many moles of KMnO4 are contained in the FB 2 run into the graduated flask.[A r: K, 39.1; O, 16.0; Mn, 54.9]

………………….. mol of KMnO4 are run into the graduated flask.

Calculate how many moles of KMnO4 are then pipetted from the 250 cm3 graduated flask into the titration flask.

………………….. mol of KMnO4 are pipetted into the titration flask.

Use this answer to calculate how many moles of iodine molecules, I2, are formed when the manganate(VII) ions react with an excess of iodide ions in the titration flask.

MnO4– + 8H+ + 5e– Mn2+ + 4H2O

I– �� I2 + e–

………………….. mol of iodine molecules, I2, are formed in the reaction.

Use this answer to calculate how many moles of sodium thiosulphate will react with the iodine molecules formed.

2S2O32– S4O6

2– + 2e–

�� I2 + e– I–

………………….. mol of thiosulphate ions react with the iodine molecules formed in the reaction.

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Calculate, to 3 significant figures, the concentration in mol dm–3 of the sodium thiosulphate, Na2S2O3, in FB 1.

The concentration of sodium thiosulphate in FB 1 is ……………….. mol dm–3.

[5]

[Total: 12]



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© UCLES 2008

2 Read through the instructions before starting the experiment.

The relative molecular mass, Mr, of a metal carbonate can be estimated by adding a weighed sample of the carbonate to a weighed excess of hydrochloric acid and measuring the mass of carbon dioxide evolved.

The tubes labelled FB 6 and FB 7 each contain the solid carbonate X2CO3. FB 8 is 2.0 mol dm–3 hydrochloric acid.

Method

(a) Follow the instructions below to determine the mass of carbon dioxide given off when X2CO3 reacts with an excess of hydrochloric acid.

• Use a measuring cylinder to transfer 75 cm3 of FB 8 into a 250 cm3 conical flask.• Weigh the flask and acid FB 8.• Weigh the tube labelled FB 6 which contains the carbonate X2CO3.• Tip the contents of the tube FB 6 into the acid in the flask, a little at a time. This

prevents loss of acid as spray from the vigorous reaction.• When the reaction appears to be complete, swirl the flask and leave to stand for

2–3 minutes, then reweigh the flask and its contents.• Reweigh the tube FB 6 and any residual carbonate not added to the acid.• Rinse out and drain the flask. • Repeat the whole experiment using tube FB 7.

In an appropriate form below record the following. • all measurements of mass made • the mass of the carbonate, X2CO3, added • the mass of carbon dioxide given off

[mass of CO2 = (initial mass of flask + acid) + (mass of carbonate) – (final mass of flask + contents)]

Results

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Calculations

(b) From your results for each experiment calculate the mass of X2CO3 that would produce 1.0 g of CO2.

With FB 6 …………………….. g of CO2 are given off from ………………… g X2CO3.

1.0 g of CO2 is given off from ………………… g X2CO3.


1.0 g of CO2 is given off from ………………… g X2CO3. [3]

(c) For each experiment calculate the relative molecular mass, M r, of X2CO3.

X2CO3(s) + 2HCl(aq) 2XCl(aq) + CO2(g) + H2O(l)

[A r: C, 12.0; O, 16.0]

M r of X2CO3 from the experiment with FB 6 is ………………………… .

M r of X2CO3 from the experiment with FB 7 is ………………………… . [1]

(d) Carbon dioxide is soluble in aqueous solutions and this can lead to an error in the molecular mass calculated.

From your observations on carrying out the experiments suggest another significant source of error. Explain the effect this will have on the measurements made and the molecular mass calculated.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]



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© UCLES 2008

(e) Some of the carbon dioxide given off in the reaction remains dissolved in the acid solution.

Suggest how you might modify the experimental method described to reduce or eliminate this error.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(f) Carry out the following instructions.

• Half fill each of two test-tubes with distilled water and place the tubes in a test-tube rack.

• To one test-tube add 1 spatula measure of powdered barium carbonate, BaCO3.• To the second test-tube add 1 spatula measure of X2CO3.• Stopper each test-tube and shake vigorously.• Half fill each of two boiling-tubes with FB 3, dilute sulphuric acid.• To one boiling-tube add 1 spatula measure of powdered barium carbonate,

BaCO3.• To the second boiling-tube add 1 spatula measure of X2CO3.• Do not attempt to stopper or shake either of these boiling-tubes.

Record your observations in the table below.

BaCO3 X2CO3

water

FB 3dilute sulphuric acid

It is suggested that sulphuric acid could be used in place of hydrochloric acid in experiments to determine the Mr of metal carbonates.

Make use of your observations and your knowledge of the chemistry of barium, to explain why the use of sulphuric acid would not be appropriate if the carbonate is barium carbonate.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

[Total: 12]



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9701/32/O/N/08© UCLES 2008

3 FB 9, FB 10 and FB 11 are aqueous solutions, each containing one of the cations listed on page 11 of the qualitative analysis notes.

You will react FB 9, FB 10 and FB 11 with aqueous sodium hydroxide, NaOH, and aqueous ammonia, NH3, to identify the cations present in each of these solutions. You will also perform tests to identify the anions present in FB 9 and FB 10.



Note that three of the cations listed on page 11 may give no precipitate with aqueous NaOH.




(a) Pour 1 cm depth of FB 9, FB 10 and FB 11 into separate test-tubes. Stand the tubes in a test-tube rack and add aqueous sodium hydroxide, NaOH, a little at a time until the reagent is in excess. Repeat the test with aqueous ammonia, NH3, as the reagent.

Record your observations in an appropriate form below.

[4]

(b) Using the observations above it is not possible to identify a single cation for any of the solutions. Use your observations and the qualitative analysis notes on page 11 to identify, for each solution, two or three cations which could be present.

FB 9 could contain the cations ....................................................................................... .

FB 10 could contain the cations ..................................................................................... .

FB 11 could contain the cations .................................................................................... .

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© UCLES 2008

(c) Use the qualitative analysis notes on page 11 to select further reagents or tests to identify precisely which cation is present in each of FB 9, FB 10 and FB 11.

Record in an appropriate form below,

• details of the reagents to be used, • the tests to be carried out, • your observations when the additional tests are carried out.

A boiling-tube must be used if any solution is to be heated.

Conclusion

FB 9 contains the cation …........................……..



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(d) FB 9 and FB 10 each contain one anion which is either a sulphate or a halide.

Use the qualitative analysis notes on page 12 to select appropriate reagents and tests to determine which anion is present in each solution.


• details of the reagents to be used, • the tests to be carried out, • your observations when the tests are carried out.

Conclusion

FB 9 contains the anion …........................……..


[6]

[Total: 16]

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9701/32/O/N/08© UCLES 2008




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/O/N/08© UCLES 2008


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)


sulphite,SO2–

3 (aq)


3 Tests for gases













SP (SC/KS) T56858/3© UCLES 2008 [Turn over







*5473604620*

CHEMISTRY 9701/32


2 hours




1

2

3

Total

Session

Laboratory



2

9701/32/O/N/08© UCLES 2008

1 You are required to find the concentration in mol dm–3 of sodium thiosulphate, Na2S2O3, in solution FB 1.

FB 1 contains sodium thiosulphate. FB 2 is potassium manganate(VII) containing 28.44 g dm–3 KMnO4. FB 3 is 1.0 mol dm–3 sulphuric acid, H2SO4. FB 4 is 10% potassium iodide containing 100 g dm–3 KI. You are also provided with starch indicator.

Dilution of FB 2

(a) By using a burette measure between 41.00 cm3 and 42.00 cm3 of FB 2 into the 250 cm3 graduated (volumetric) flask labelled FB 5.



Titration

Fill a second burette with FB 1, the solution containing sodium thiosulphate.

Use a measuring cylinder to transfer 10 cm3 of FB 3 and 10 cm3 of FB 4 into a conical flask. Pipette 25.0 cm3 of FB 5 into the conical flask containing the mixture of FB 3 and FB 4. The potassium manganate(VII) oxidises potassium iodide to iodine, I2.

Titrate the liberated iodine with FB 1 as follows. Run the solution from the burette into the conical flask until the initial red/brown colour of the iodine becomes pale yellow. Then add 1 cm3 of the starch indicator and continue to add FB 1 drop by drop until the blue/black colour of the starch/iodine complex disappears, leaving a colourless solution. This is the end-point of the titration.



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The volume of FB 1 is …………….. cm3. [1]

Calculations


(c) Calculate how many moles of KMnO4 are contained in the FB 2 run into the graduated flask.[A r: K, 39.1; O, 16.0; Mn, 54.9]

………………….. mol of KMnO4 are run into the graduated flask.

Calculate how many moles of KMnO4 are then pipetted from the 250 cm3 graduated flask into the titration flask.

………………….. mol of KMnO4 are pipetted into the titration flask.

Use this answer to calculate how many moles of iodine molecules, I2, are formed when the manganate(VII) ions react with an excess of iodide ions in the titration flask.

MnO4– + 8H+ + 5e– Mn2+ + 4H2O

I– �� I2 + e–

………………….. mol of iodine molecules, I2, are formed in the reaction.

Use this answer to calculate how many moles of sodium thiosulphate will react with the iodine molecules formed.

2S2O32– S4O6

2– + 2e–

�� I2 + e– I–

………………….. mol of thiosulphate ions react with the iodine molecules formed in the reaction.

ForExaminer’s

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9701/32/O/N/08

ForExaminer’s

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© UCLES 2008

Calculate, to 3 significant figures, the concentration in mol dm–3 of the sodium thiosulphate, Na2S2O3, in FB 1.

The concentration of sodium thiosulphate in FB 1 is ……………….. mol dm–3.

[5]

[Total: 12]



5


ForExaminer’s

Use

© UCLES 2008

2 Read through the instructions before starting the experiment.

The relative molecular mass, Mr, of a metal carbonate can be estimated by adding a weighed sample of the carbonate to a weighed excess of hydrochloric acid and measuring the mass of carbon dioxide evolved.

The tubes labelled FB 6 and FB 7 each contain the solid carbonate X2CO3. FB 8 is 2.0 mol dm–3 hydrochloric acid.

Method

(a) Follow the instructions below to determine the mass of carbon dioxide given off when X2CO3 reacts with an excess of hydrochloric acid.

• Use a measuring cylinder to transfer 75 cm3 of FB 8 into a 250 cm3 conical flask.• Weigh the flask and acid FB 8.• Weigh the tube labelled FB 6 which contains the carbonate X2CO3.• Tip the contents of the tube FB 6 into the acid in the flask, a little at a time. This

prevents loss of acid as spray from the vigorous reaction.• When the reaction appears to be complete, swirl the flask and leave to stand for

2–3 minutes, then reweigh the flask and its contents.• Reweigh the tube FB 6 and any residual carbonate not added to the acid.• Rinse out and drain the flask. • Repeat the whole experiment using tube FB 7.

In an appropriate form below record the following. • all measurements of mass made • the mass of the carbonate, X2CO3, added • the mass of carbon dioxide given off

[mass of CO2 = (initial mass of flask + acid) + (mass of carbonate) – (final mass of flask + contents)]

Results

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© UCLES 2008

Calculations

(b) From your results for each experiment calculate the mass of X2CO3 that would produce 1.0 g of CO2.


1.0 g of CO2 is given off from ………………… g X2CO3.


1.0 g of CO2 is given off from ………………… g X2CO3. [3]

(c) For each experiment calculate the relative molecular mass, M r, of X2CO3.

X2CO3(s) + 2HCl(aq) 2XCl(aq) + CO2(g) + H2O(l)

[A r: C, 12.0; O, 16.0]

M r of X2CO3 from the experiment with FB 6 is ………………………… .

M r of X2CO3 from the experiment with FB 7 is ………………………… . [1]

(d) Carbon dioxide is soluble in aqueous solutions and this can lead to an error in the molecular mass calculated.

From your observations on carrying out the experiments suggest another significant source of error. Explain the effect this will have on the measurements made and the molecular mass calculated.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]



7


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© UCLES 2008

(e) Some of the carbon dioxide given off in the reaction remains dissolved in the acid solution.

Suggest how you might modify the experimental method described to reduce or eliminate this error.

..........................................................................................................................................

..........................................................................................................................................

......................................................................................................................................[1]

(f) Carry out the following instructions.

• Half fill each of two test-tubes with distilled water and place the tubes in a test-tube rack.

• To one test-tube add 1 spatula measure of powdered barium carbonate, BaCO3.• To the second test-tube add 1 spatula measure of X2CO3.• Stopper each test-tube and shake vigorously.• Half fill each of two boiling-tubes with FB 3, dilute sulphuric acid.• To one boiling-tube add 1 spatula measure of powdered barium carbonate,

BaCO3.• To the second boiling-tube add 1 spatula measure of X2CO3.• Do not attempt to stopper or shake either of these boiling-tubes.

Record your observations in the table below.

BaCO3 X2CO3

water

FB 3dilute sulphuric acid

It is suggested that sulphuric acid could be used in place of hydrochloric acid in experiments to determine the Mr of metal carbonates.

Make use of your observations and your knowledge of the chemistry of barium, to explain why the use of sulphuric acid would not be appropriate if the carbonate is barium carbonate.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]

[Total: 12]



8

9701/32/O/N/08© UCLES 2008

3 FB 9, FB 10 and FB 11 are aqueous solutions, each containing one of the cations listed on page 11 of the qualitative analysis notes.

You will react FB 9, FB 10 and FB 11 with aqueous sodium hydroxide, NaOH, and aqueous ammonia, NH3, to identify the cations present in each of these solutions. You will also perform tests to identify the anions present in FB 9 and FB 10.



Note that three of the cations listed on page 11 may give no precipitate with aqueous NaOH.




(a) Pour 1 cm depth of FB 9, FB 10 and FB 11 into separate test-tubes. Stand the tubes in a test-tube rack and add aqueous sodium hydroxide, NaOH, a little at a time until the reagent is in excess. Repeat the test with aqueous ammonia, NH3, as the reagent.

Record your observations in an appropriate form below.

[4]

(b) Using the observations above it is not possible to identify a single cation for any of the solutions. Use your observations and the qualitative analysis notes on page 11 to identify, for each solution, two or three cations which could be present.

FB 9 could contain the cations ....................................................................................... .

FB 10 could contain the cations ..................................................................................... .

FB 11 could contain the cations .................................................................................... .

[2]

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9


ForExaminer’s

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© UCLES 2008

(c) Use the qualitative analysis notes on page 11 to select further reagents or tests to identify precisely which cation is present in each of FB 9, FB 10 and FB 11.


• details of the reagents to be used, • the tests to be carried out, • your observations when the additional tests are carried out.

A boiling-tube must be used if any solution is to be heated.

Conclusion




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© UCLES 2008

(d) FB 9 and FB 10 each contain one anion which is either a sulphate or a halide.

Use the qualitative analysis notes on page 12 to select appropriate reagents and tests to determine which anion is present in each solution.


• details of the reagents to be used, • the tests to be carried out, • your observations when the tests are carried out.

Conclusion



[6]

[Total: 16]

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9701/32/O/N/08© UCLES 2008




ionreaction with

NaOH(aq) NH3(aq)

aluminium,Al 3+(aq)



ammonium,NH

+4 (aq)


barium,Ba2+(aq)


calcium,Ca2+(aq)





copper(II),Cu2+(aq)



iron(II),Fe2+(aq)



iron(III),Fe3+(aq)



lead(II),Pb2+(aq)



magnesium,Mg2+(aq)






zinc,Zn2+(aq)






12

9701/32/O/N/08© UCLES 2008


ion reaction

carbonate,CO2–

3



4(aq)


chloride,Cl –(aq)


bromide,Br –(aq)


iodide,I– (aq)


nitrate,NO–


nitrite,NO–


sulphate,SO2–

4 (aq)


sulphite,SO2–

3 (aq)


3 Tests for gases













SJF4880/SJF 17555/2© UCLES 2009 [Turn over







*5014492689*

CHEMISTRY 9701/31


2 hours




1

2

Total

Session

Laboratory



2

9701/31/O/N/09© UCLES 2009

BLANK PAGE



3


ForExaminer’s

Use

1 You are provided with the following reagents.

• two weighing bottles labelled FA 1, each containing between 2.90 g and 3.00 g of zinc powder

• FA 2, 0.80 mol dm–3 copper sulfate, CuSO4

You are to determine the enthalpy change, ∆H, for the following reaction.

Zn(s) + CuSO4(aq) Cu(s) + ZnSO4(aq)

You will carry out the experimental procedure twice.

Read through the instructions below before starting the experiment.

(a) You will weigh each bottle and later in the experiment weigh it again after the zinc powder has been tipped into copper sulfate solution.

In the space below prepare a table to record the weighings and the mass of zinc powder used in each experiment.

Weigh accurately, to at least one decimal place, one of the weighing bottles labelledFA 1.

Record this mass in the table you have prepared. [1]

(b) Procedure

• Support the plastic cup in the 250 cm3 beaker and, using a pipette, place 25.0 cm3 of FA 2 into the plastic cup.

• Stir gently, taking a temperature reading every ½ minute until a steady temperature has been obtained for a period of at least 2 minutes. You may need to tilt the beaker in order to cover the bulb of the thermometer with solution.

• On a precise minute reading tip the zinc powder from the weighing bottle into the plastic cup.

Do not read the temperature at this time or at the following ½ minute.

• Continue to stir the mixture thoroughly. Starting 1 minute after the addition of the zinc powder, record the temperature every ½ minute until the temperature has reached a maximum value and then decreased steadily for at least 5 minutes.

• Reweigh the empty weighing bottle. Record the mass of the bottle + any residual zinc powder and the mass of zinc powder used in the experiment in the table you prepared in (a).

• Record your results in an appropriate form in the space on the following page.

Repeat the experiment using the contents of the second weighing bottle and 25.0 cm3 copper sulfate solution pipetted into a clean plastic cup.



4

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ForExaminer’s

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(b) continued

Results Make certain your readings of temperature display the precision of the apparatus used.

[11]

(c) Plot your temperature and time readings separately for each experiment on the grids on the next page. Your temperature axis should extend 10 °C above the highest temperature you recorded.

Draw lines as instructed below.

On each graph draw a horizontal straight line through the steady initial temperature.

Extrapolate the cooling section of each graph back to the time when you added the zinc powder.

Draw construction lines on the graphs to deduce the “theoretical” temperature rise at the moment of mixing the reagents.



5


ForExaminer’s

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[4]



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ForExaminer’s

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(d) The “theoretical” temperature rises are ……………… °C and ……………… °C.

The mean “theoretical” temperature rise is ……………… °C. [1]

Calculations

Show working and appropriate significant figures in all of your calculations. [2]

(e) Calculate how many moles of copper sulfate, CuSO4, were pipetted into the plastic cup.

……………… mol of CuSO4 were pipetted into the cup

For each experiment calculate how many moles of zinc powder were added to the plastic cup.

[Ar: Zn, 65.4]

1st experiment 2nd experiment

In the 1st experiment ……………… mol of zinc powder were added to the plastic cup.

In the 2nd experiment ……………… mol of zinc powder were added to the plastic cup. [1]

(f) Use your answers to (e) and the equation for the reaction to determine which reagent was in excess and which was the limiting reagent. Explain your answer.


..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]



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(g) From your mean “theoretical” temperature rise at the time of mixing, calculate the heat energy released in the plastic cup by the reaction of zinc powder with copper sulfate solution.

[You may assume that 4.3 J are required to raise the temperature of 1 cm3 of any solution by 1 °C and that the mass of any solid may be ignored.]

……………… …… of heat energy are released. [1]

(h) Calculate, correct to 3 significant figures, the enthalpy change in kJ mol–1 for the following reaction.


∆H = ……………………………… kJ mol–1

[2]

(i) Identify and explain one source of error in the experiment you have carried out.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]

(j) Suggest a way in which the experimental method you used could be improved in a school or college laboratory in order to minimise this error.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]

[Total: 26]



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ForExaminer’s

Use

2 The three boiling-tubes, labelled FA 3, FA 4, and FA 5, each contain a solid with one cation and one anion from those listed on pages 11 and 12.

You will carry out specified tests to deduce the cations and anions present in FA 3, FA 4 and FA 5.

At each stage of any test you are to record details of the following. • colour changes seen • the formation of any precipitate • the solubility of such precipitates in an excess of the reagent added


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed a boiling-tube MUST be used.

(a) Heat the boiling-tube containing FA 5 gently at first then more strongly. Record your observations in the space below.

[2]

(b) In their boiling-tubes, dissolve FA 3, FA 4 and the cold residue after heating FA 5 in a minimum of dilute nitric acid and then add distilled water so that each boiling-tube is approximately ²⁄³ full. Warm to dissolve if necessary.

Record your observations in the space below. Use these solutions for tests (d), (e) and (f).

[1]



9


ForExaminer’s

Use

(c) Which anion can be identified from your observations in (a) and (b)? Explain your answer.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]

(d) The cations present in FA 3, FA 4 and FA 5 can be identified by reaction of each solution with aqueous sodium hydroxide and with aqueous ammonia.

React 1 cm depth of each of the solutions prepared in (b) with each of these two reagents.

Record, in an appropriate form in the space below, your observations for these reactions.

Conclusions

Using your observations you should be able to identify the cation present in two of the solutions. For the remaining solution you should be able to identify two possible cations.

FA 3 contains the cation(s) ……………………………… .

FA 4 contains the cation(s) ……………………………… .

FA 5 contains the cation(s) ……………………………… .[6]

i

ii

iii

iv

v

vi



10

9701/31/O/N/09© UCLES 2009

ForExaminer’s

Use

(e) Use the information on pages 11 and 12 to select a reagent to distinguish between the two possible cations identified as present in one of the solutions in (d).

Carry out the test with the selected reagent.

reagent .............................................................................................................................

observation ......................................................................................................................

conclusion ........................................................................................................................ [2]

(f) Carry out the following tests.

testobservations

FA 3 FA 4 FA 5

To 1 cm depth of solution in a test-tube, add 1 cm depth of aqueous barium nitrate,

then

add 2 cm depth of dilute nitric acid.

To 1 cm depth of solution in a test-tube, add 1 cm depth of aqueous silver nitrate,

then

allow any precipitate formed to settle, pour off the solution and add aqueous ammonia to the precipitate.

What conclusions can be made from the observations above?

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [2]

[Total: 14]



11





reaction with

NaOH(aq) NH3(aq)

aluminium,

Al3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,

Ba2+(aq)


calcium,

Ca2+(aq)


chromium(III),

Cr3+(aq)



grey-green ppt.

insoluble in excess

copper(II),

Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),

Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),

Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),

Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),

Mn2+(aq)


insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




12

9701/31/O/N/09© UCLES 2009


ion reaction

carbonate,CO3


chromate(VI),CrO4

2– (aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl– (aq)


bromide,Br– (aq)


iodide,I– (aq)


nitrate,NO3


nitrite,NO2

– (aq)NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulfate,SO4


sulfite,SO3


3 Tests for gases













DC (SJF4887/CG) 17559/3© UCLES 2009 [Turn over







*0830907008*

CHEMISTRY 9701/32


2 hours




1

2

Total

Session

Laboratory



2

9701/32/O/N/09© UCLES 2009

ForExaminer’s

Use

1 This question concerns the solubility of FB 1, potassium nitrate, in water.

The solubility of a substance in water is defined as:the mass of substance that will dissolve in and just saturate 100 g of water at a particular temperature.When a solution is saturated the dissolved solid is in equilibrium with undissolved solid.When a solution of potassium nitrate is cooled it becomes saturated when crystals form in the solution.

You are to investigate how the solubility of FB 1 in water varies with temperature.

You are provided with the following materials. weighing bottle, labelled FB 1, containing potassium nitrate distilled water

Read through the instructions before starting any practical work.

Method

• Weigh an empty boiling-tube.

• Add the contents of the weighing bottle labelled FB 1 to the weighed boiling-tube.

• Reweigh the boiling-tube and its contents.

• Record, in an appropriate form below, your weighings and the mass of FB 1 used.

(a) Weighings

[2]



3


(b) Preparing a saturated solution

• Fill the burette with distilled water.

• Add 14.00 cm3 of distilled water from the burette to the weighed boiling-tube containingFB 1.

• Use the clamp as a holder for the boiling-tube. Take care not to break the tube by clamping it too tightly.

• Warm the tube carefully, while stirring the contents with a thermometer, until all the solid has dissolved. (Take care that you do not break the thermometer bulb or the tube while stirring.)

• Keeping the tube in the clamp attach the clamp to a stand.

• Let the tube cool and continue to stir gently with the thermometer.

• Watch the solution carefully. Note and record (on the next page) the temperature at which you first notice crystals forming in the solution.

• If you are uncertain about the temperature when crystals first form, warm the tube again for a few moments and repeat the cooling.

• As soon as you have recorded the temperature add a further 2.00 cm3 of distilled water to the tube from the burette.

• Warm to redissolve the solid and cool as before.

• Note and record (on the next page) the temperature at which crystals now form in the solution. This will be lower than the temperature obtained with 14.00 cm3 of water.

• Repeat the addition of 2.00 cm3 of distilled water, the heating and the cooling, until you have four readings in total.



4

9701/32/O/N/09© UCLES 2009

ForExaminer’s

Use

(c) In an appropriate form in the space below, record the following.

• the total volume of distilled water in the boiling-tube

• the temperature at which crystals first appeared for each solution

Make certain that your results show the precision of your working.

[8]

(d) For each solution, calculate the solubility (in grams of solid per 100 g of water) using the following formula.

solubility = 100volume of water

× mass of FB 1 dissolved

Complete the table below to show the solubility at different temperatures. In all calculated values show appropriate significant figures.

solubility

(in grams of solid per100 g of water)

temperature/ °C

[3]

i

ii

iii

iv

v

vi

vii

viii



5


ForExaminer’s

Use

(e) Plot solubility against temperature and draw an appropriate line through the points plotted. Do not start at zero on either axis. You will need to be able to find the solubility of FB1 at 42.5°C.



6

9701/32/O/N/09© UCLES 2009

ForExaminer’s

Use

From the graph plotted the solubility of FB 1 in water at 42.5 °C is

…………….. g of solid per 100 g of water.[6]

(f) Describe how the solubility of FB 1 changes with temperature.

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]

(g) Use your answer to (f) and your understanding of equilibrium systems to explain if dissolving FB 1, KNO3, under equilibrium conditions is exothermic or endothermic.

KNO3(s) + aq KNO3(aq)

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [2]

(h) Suggest two possible sources of inaccuracy, other than poor experimental technique, in this experiment.

1 .......................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

2 .......................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................[2]



7


ForExaminer’s

Use

(i) A solution of KNO3, saturated at 60 °C, is prepared in a thermostatically controlled water bath.

The solubility of KNO3 at 60 °C can be calculated if the mass of the solution and the mass of solid dissolved in the solution can be determined.

Suggest steps to enable you to find these masses. You may not need all of these numbered steps.

1 .......................................................................................................................................

2 .......................................................................................................................................

3 .......................................................................................................................................

4 .......................................................................................................................................

5 .......................................................................................................................................

6 .......................................................................................................................................

7 .......................................................................................................................................

Show how you would calculate the solubility of KNO3 at 60 °C from the mass of the solution and the mass of solid dissolved in the solution.

[2]

[Total: 26]



8

9701/32/O/N/09© UCLES 2009

ForExaminer’s

Use

2 You are provided with three solids, FB 2, FB 3, and FB 4. Each of the solids contains one cation from those on page 11 and a sulfite or sulfate anion.

You will carry out specified tests to identify the cations and anions present in FB 2, FB 3 and FB 4. Use the data on pages 11 and 12.

At each stage of any test you are to record details of the following.• colour changes seen• the formation of any precipitate• the solubility of such precipitates in an excess of the reagent added


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed a boiling-tube MUST be used.

(a) In separate boiling-tubes, dissolve half of each of the solids FB 2, FB 3 and FB 4 in a minimum volume of dilute hydrochloric acid.

Gently warm each of the boiling-tubes. Add distilled water so that each boiling-tube is approximately 2/3 full. Record your observations in an appropriate form in the space below.

[2]

(b) The cations present in FB 2, FB 3 and FB 4 can be identified by reaction of each solution, with aqueous sodium hydroxide and with aqueous ammonia.

React 1 cm depth of each of the solutions prepared in (a) with each of these two reagents.

Record, in an appropriate form, in the space below your observations for these reactions. i

ii

iii

iv

v



9


ForExaminer’s

Use

Conclusions

Using your observations you should be able to identify the cation in two of the solutions. For the remaining solution you should be able to identify two possible cations.

FB 2 contains the cation(s) ………………………………. .

FB 3 contains the cation(s) ………………………………. .

FB 4 contains the cation(s) ………………………………. . [5]

(c) Use the information on pages 11 and 12 to select a reagent to distinguish between the two possible cations identified as present in one of the solutions in (b).

..........................................................................................................................................

Carry out the test with the selected reagent.

observation ......................................................................................................................

conclusion ........................................................................................................................[1]

(d) In separate boiling-tubes shake the remaining half of each solid with 3 cm depth of distilled water.

If any solid does not readily dissolve in water filter the mixture and retain the solution formed.

You will need to keep some of the FB 2 solution for test (f). Carry out the following tests.

test observations

FB 2 FB 3 FB 4

To 1 cm depth of the solution in a test-tube, add 1 cm depth of aqueous barium chloride,

then,

add 2 cm depth of dilute hydrochloric acid.

Draw appropriate conclusions as to the identity of the anion in each solution.

FB 2 contains the anion ………………………………. .

FB 3 contains the anion ………………………………. .

FB 4 contains the anion ………………………………. . [3]



10

9701/32/O/N/09© UCLES 2009

ForExaminer’s

Use

(e) Explain why aqueous barium chloride must be added before hydrochloric acid when distinguishing between a sulfite and a sulfate.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [1]

(f) Carry out the following test with the solution of FB 2 prepared in (d).

test observation

To 1 cm depth of the solution of FB 2 in a test-tube add 1 cm depth of aqueous potassium iodide,

then

add a few drops of starch solution.

What is the nature of the reaction taking place between FB 2 and potassium iodide?

..........................................................................................................................................

..........................................................................................................................................

..................................................................................................................................... [2]

[Total: 14]



11





reaction with

NaOH(aq) NH3(aq)

aluminium,

Al3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,

Ba2+(aq)


calcium,

Ca2+(aq)


chromium(III),

Cr3+(aq)



grey-green ppt.

insoluble in excess

copper(II),

Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),

Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),

Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),

Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),

Mn2+(aq)


insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




12

9701/32/O/N/09© UCLES 2009


ion reaction

carbonate,CO3


chromate(VI),CrO4

2– (aq)yellow solution turns orange with H+(aq);gives yellow ppt. with Ba2+(aq);gives bright yellow ppt. with Pb2+(aq)

chloride,Cl– (aq)


bromide,Br– (aq)


iodide,I– (aq)


nitrate,NO3


nitrite,NO2

– (aq)NH3 liberated on heating with OH–(aq) and Al foil,NO liberated by dilute acids(colourless NO → (pale) brown NO2 in air)

sulfate,SO4


sulfite,SO3


3 Tests for gases













DC (SJF5336) 11751/4© UCLES 2009 [Turn over







*7346664655*

CHEMISTRY 9701/33


2 hours




1

2

3

Total

Session

Laboratory



2

9701/33/O/N/09

BLANK PAGE



3


ForExaminer’s

Use



• FA 1, hydrated iron(II) sulfate • FA 2, aqueous iron(II) sulfate • FA 3, aqueous potassium manganate(VII) • FA 4, sulfuric acid

The formula of hydrated iron(II) sulfate is FeSO4.xH2O where x shows the number of molecules of water of crystallisation present.

The value of x can be found by two different methods.

Method 1 involves heating to drive off water of crystallisation while Method 2 uses a titration to determine the concentration of Fe2+(aq).

(a) Method 1

• Weigh a crucible and record the mass. • Add between 1.80 g and 2.00 g of FA 1 and record the new mass. • Place the crucible containing FA 1 on a pipe clay triangle and heat gently for about

four minutes with a Bunsen burner. • Allow the crucible to cool. You should continue with Method 2 while the crucible is

cooling. • Weigh the crucible and its contents.

Record all masses in the space below.

[3]

(b) Calculate the mass of water lost and the mass of iron(II) sulfate that remained after heating.

mass of water lost = …………… g

mass of iron(II) sulfate remaining = …………… g [1]



4

9701/33/O/N/09© UCLES 2009

ForExaminer’s

Use

(c) Use your answer to (b) to calculate how many moles of water were lost and the moles of iron(II) sulfate, FeSO4, remaining after heating.

Show all of your working. [Ar : Fe, 55.8; H, 1.0; O, 16.0; S, 32.1]

The hydrated iron(II) sulfate contained …………………………… mol of water

and …………………………… mol of FeSO4. [2]

(d) Use your answer to (c) to determine the value of x in the formula of hydrated iron(II) sulfate, FeSO4.xH2O.

x = ……………….. [2]

(e) Method 2

• Fill the burette with FA 3, aqueous potassium manganate(VII). • Pipette 25.0 cm3 of FA 2 into a conical flask and use a measuring cylinder to add

approximately 20 cm3 of FA 4. • Titrate this solution with FA 3 from the burette until the first permanent pink colour

remains in the solution. • Perform sufficient further titrations to obtain accurate results. • Record your titration results in the space below. Make certain that your recorded

results show the precision of your working.

Summary 25.0 cm3 of FA 2 reacted with ………….……. cm3 of FA 3.

Show which results you used to obtain the value of the volume of FA 3 by placing a tick (✓) under the readings used in your results. [11]

i

ii

iii

iv

v

vi

vii

viii

ix

x

xi



5


ForExaminer’s

Use

(f) All experimental methods contain errors, some of which are concerned with uncertainty of measurements.

Complete the table below to show the uncertainties in measuring the volume of potassium manganate(VII) used in Method 2.

maximum uncertainty in a single reading with a burette ……………… cm3

volume of potassium manganate(VII), FA 3, from the summary in (e) ……………… cm3

maximum percentage error in the volume of potassium manganate(VII) used ……………… % [2]

(g) Method 1 is usually less accurate than Method 2 for finding the value of x in the formula of hydrated iron(II) sulfate, FeSO4.xH2O.

A group of students carried out Method 1 correctly but calculated a value of 9 for x. The true value for x is 7.

Suggest an error in the practical procedure of the experiment that could account for this difference.

..........................................................................................................................................

...................................................................................................................................... [1]

(h) Suggest a modification that could be made to the practical procedure in Method 1 to reduce this error.

Explain why this modification should give an answer nearer to 7.

modification ......................................................................................................................

..........................................................................................................................................

explanation ......................................................................................................................

..................................................................................................................................... [2]

[Total: 24]

BEFORE STARTING QUESTION 2, heat a half-full 250 cm3

beaker of water for use as a hot water-bath in question 3.



6

9701/33/O/N/09© UCLES 2009

ForExaminer’s

Use

2 The four solutions FA 5, FA 6, FA 7 and FA 8 each contain one of the following anions.

• chloride, Cl –

• iodide, I–

• nitrate, NO3–

• nitrite, NO2–

Use information from the Qualitative Analysis Notes on page 11 to answer the following questions.

(a) Which single reagent could you use to identify the solution containing the nitrite ion?

..........................................................................................................................................

Which single reagent could you use to identify the solutions containing the chloride and the iodide ion?

...................................................................................................................................... [1]

(b) Use the reagents selected in (a) to test each of the solutions.


Record in an appropriate form in the space below, the reagents used and the observations made.

From your observations identify the solutions containing chloride, iodide and nitrite ions. In each case give evidence to support your answer.

solution ……………… contains the chloride ion.


solution ……………… contains the iodide ion.


solution ……………… contains the nitrite ion.

supporting evidence ................................................................................................... [7]

i

ii

iii

iv

v

vi

vii



7


ForExaminer’s

Use

(c) Do not carry out this test.

State another test that you could use to confirm the presence of chloride and iodide ions.

..........................................................................................................................................

...................................................................................................................................... [1]

[Total: 9]



8

9701/33/O/N/09© UCLES 2009

ForExaminer’s

Use

3 (a) You are to carry out the tests given in the table below on solutions FA 9 and FA 10. You should record details of colour changes seen and the formation of any precipitate.


Reheat your water bath until the water boils. Turn off the Bunsen burner.

test observations

(i) To 1 cm depth of FA 9 in a test-tube, add 1 cm depth of dilute hydrochloric acid.

(ii) To 1 cm depth of FA 9 in a test-tube, add 1 cm depth of dilute sulfuric acid.

(iii) To 1 cm depth of FA 10 in a boiling-tube, add dilute sulfuric acid until no further change occurs.

Use this solution for test (iv).

(iv) To the solution left after test (iii) add 1 cm depth of ethanol.

Place the mixture in your hot water bath and leave for approximately 3 minutes.

(v) To 1cm depth of FA 9 in a test-tube add 1 cm depth of FA 10.

[4]



9


ForExaminer’s

Use

(b) From your observations in (a) identify the cation present in FA 9. Give evidence to support your answer.

Solution FA 9 contains the ……………… ion.


...................................................................................................................................... [2]

(c) What chemical change, involving ethanol, takes place in reaction (iv)? Give evidence to support your answer.

chemical change ..............................................................................................................


...................................................................................................................................... [1]

[Total: 7]



10

9701/33/O/N/09© UCLES 2009




reaction with

NaOH(aq) NH3(aq)

aluminium,

Al3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,


chromium(III),

Cr3+(aq)



grey-green ppt.

insoluble in excess

copper(II),

Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),

Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),

Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),

Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),

Mn2+(aq)


insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




11

9701/33/O/N/09© UCLES 2009


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)

yellow soln turns orange with H+(aq);



chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)

gives yellow ppt. with Ag+(aq) (insoluble In NH3(aq));


nitrate,

NO3– (aq)


nitrite,

NO2– (aq)

NH3 liberated on heating with OH–(aq) and Al foil,

NO liberated by dilute acids(colourless NO (pale) brown NO2 in air)

sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid);


sulfite,

SO32– (aq)



3 Tests for gases










12

9701/33/O/N/09



BLANK PAGE




DC (SJF5337) 11762/3© UCLES 2009 [Turn over

*8512416568*







CHEMISTRY 9701/34


2 hours




1

2

3

Total

Session

Laboratory



2

9701/34/O/N/09

BLANK PAGE



3


ForExaminer’s

Use



• FB 1, hydrated copper(II) sulfate • FB 2, aqueous copper(II) sulfate • FB 3, aqueous sodium thiosulfate • FB 4, aqueous potassium iodide • FB 5, starch indicator solution

The formula of hydrated copper(II) sulfate is CuSO4.xH2O where x shows the number of molecules of water of crystallisation present.

The value of x can be found by two different methods. Method 1 involves heating to drive off water of crystallisation while Method 2 uses a titration

to determine the concentration of Cu2+(aq).

(a) Method 1

• Weigh a crucible and record the mass. • Add between 2.50 g and 2.70 g of FB 1 and record the new mass. • Place the crucible containing FB 1 on a pipe clay triangle and heat gently for about

four minutes with a Bunsen burner. • Allow the crucible to cool. You should continue with Method 2 while the crucible is

cooling. • Weigh the crucible and its contents.

Record all masses in the space below.

[3]

(b) Calculate the mass of water lost and the mass of copper(II) sulfate that remained after heating.

mass of water lost = …………… g

mass of copper(II) sulfate remaining = …………… g[1]



4

9701/34/O/N/09© UCLES 2009

ForExaminer’s

Use

(c) Use your answer to (b) to calculate how many moles of water were lost and the moles of copper(II) sulfate, CuSO4, remaining after heating.

Show all of your working. [Ar : Cu, 63.5; H, 1.0; O, 16.0; S, 32.1]

The hydrated copper(II) sulfate contained …………………………… mol of water

and …………………………… mol of CuSO4. [2]

(d) Use your answer to (c) to determine the value of x in the formula of hydrated copper(II) sulfate, CuSO4.xH2O.

x = ……………….. [2]

(e) Method 2

• Fill the burette with FB 3, aqueous sodium thiosulfate. • Pipette 25.0 cm3 of FB 2 into a conical flask and use a measuring cylinder to add

10 cm3 of FB 4. • Titrate this solution with FB 3 from the burette until the mixture becomes yellow-

brown. Do not add too much FB 3 at this stage. • An off-white precipitate is also present in the flask and this will mask the colour of

the solution. • Add approximately 1 cm3 of FB 5. The solution will become blue-black as a starch

iodine complex is formed. • Continue the titration until the blue-black colour of the complex just disappears

leaving the off-white precipitate. • Perform sufficient further titrations to obtain accurate results. • Record your titration results in the space below. Make certain that your recorded

results show the precision of your working.

Summary 25.0 cm3 of FB 2 reacted with ………….……. cm3 of FB 3.

Show which results you used to obtain the value of the volume of FB 3 by placing a tick (✓) under the readings used in your results. [11]

i

ii

iii

iv

v

vi

vii

viii

ix

x

xi



5


ForExaminer’s

Use

(f) (i) In Method 1 a student was advised to carry out all weighings using the same balance. What type of error might be introduced if more than one balance was used?

..................................................................................................................................

..............................................................................................................................[1]

(ii) In Method 2, 10 cm3 of FB 4 was added during the titration process. Assume that the measuring cylinder used could be read to ± 0.5 cm3. Calculate the percentage error in the measurement of this volume.

………….. % error [1]

(g) Method 1 is usually less accurate than Method 2 for finding the value of x in the formula of hydrated copper(II) sulfate, CuSO4.xH2O.

A group of students carried out Method 1 correctly but calculated a value of 4 for x. The true value for x is 5.

Suggest an error in the practical procedure of the experiment that could account for this difference.

.........................................................................................................................................

..................................................................................................................................... [1]

(h) Suggest a modification that could be made to the practical procedure in Method 1 to reduce this error.

Explain why this modification should give an answer nearer to 5.

modification .....................................................................................................................

.........................................................................................................................................

explanation .....................................................................................................................

.................................................................................................................................... [2]

[Total: 24]



6

9701/34/O/N/09© UCLES 2009

ForExaminer’s

Use

2 In this question you should use information from the Qualitative Analysis Notes on pages 9 and 10.

(a) Solutions FB 6, FB 7 and FB 8 are known to be either chlorides or sulfates of aluminium, magnesium or calcium. The addition of aqueous sodium hydroxide and aqueous ammonia can be used to give information about the cation present.

Add NaOH(aq) and NH3(aq) separately to each of the solutions FB 6, FB 7 and FB 8.


Record both the tests and your observations in an appropriate form in the space below.

From your observations identify the solutions containing aluminium, magnesium and calcium ions. In each case give evidence to support your answer.

Solution ……………… contains the aluminium ion.

supporting evidence .......................................................................................................

Solution ……………… contains the magnesium ion.

supporting evidence .......................................................................................................

Solution ……………… contains the calcium ion.

supporting evidence ................................................................................................... [7]

i

ii

iii

iv

v

vi

vii



7


ForExaminer’s

Use

(b) Choose a pair of reagents that, used together, would identify which solution or solutions contain(s) the sulfate ion.

Carry out the tests and record, in the space below, the reagents used and the observations made.

The sulfate ion is present in …………………………… . [2]

[Total: 9]



8

9701/34/O/N/09© UCLES 2009

ForExaminer’s

Use

3 (a) You are to carry out the tests given in the table below on solid FB 9.

Record details of any gases that are released in the reactions. These gases should be identified by a test, described in the appropriate part of the table.


test observations

(i) Place a spatula measure of FB 9 in the small hard-glass test-tube labelled FB 9 and heat the solid strongly.

(ii) To 1 cm depth of aqueous sodium hydroxide in a boiling-tube, add 1 spatula measure of FB 9,

then

gently heat the mixture, do not boil

Care is needed when heating aqueous sodium hydroxide.

(iii) To 1 cm depth of aqueous sodium hydroxide in a boiling-tube, add 1 spatula measure of FB 9 and a piece of aluminium foil,

then

gently heat the mixture.

Care is needed when heating aqueous sodium hydroxide. [4]

(b) What elements must be present in FB 9 to give the results you have obtained in test (i) and test (iii)?

..................................................................................................................................... [1]

(c) What is the function of the aluminium foil in test (iii)?

..................................................................................................................................... [1]

(d) Do not carry out this test What would you expect to see if 1 cm depth of dilute hydrochloric acid was added to a

spatula measure of FB 9?

.........................................................................................................................................

..................................................................................................................................... [1]

[Total: 7]



9





reaction with

NaOH(aq) NH3(aq)

aluminium,

Al3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,


chromium(III),

Cr3+(aq)



grey-green ppt.

insoluble in excess

copper(II),

Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),

Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),

Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),

Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),

Mn2+(aq)


insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




10

9701/34/O/N/09© UCLES 2009


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)

yellow soln turns orange with H+(aq);



chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)

gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid);


sulfite,

SO32– (aq)



3 Tests for gases










11

9701/34/O/N/09

BLANK PAGE



12

9701/34/O/N/09



BLANK PAGE




DC (CW/SW) 28271/4© UCLES 2010 [Turn over







*3933279290*

CHEMISTRY 9701/31

Advanced Practical Skills October/November 2010

2 hours



Session

Laboratory


1

2

3

Total



2

9701/31/O/N/10© UCLES 2010

ForExaminer’s

Use

There are three questions on this paper. Question 2 should not be the last question attempted.

1 You are to determine the concentration of hydrochloric acid, which supplies the H+ ions in the following reaction.

IO3–(aq) + 5I–(aq) + 6H+(aq) 3H2O(l) + 3I2(aq)

In the presence of an excess of IO3– ions and an excess of I– ions, the amount of I2 liberated

is directly proportional to the amount of H+ ions present and can be determined by titration with sodium thiosulfate, Na2S2O3.

You are provided with the following reactants.

FA 1 hydrochloric acid FA 2 contai ning 15.0 g dm–3 sodium thiosulfate, Na2S2O3.5H2O aqueous potassium iodate(V), KIO3 aqueous potassium iodide, KI

(a) Method

• Fill a burette with FA 2. • Pipette 25.0 cm3 of FA 1 into the conical flask. • Use a 25 cm3 measuring cylinder to add to the flask 10 cm3 of aqueous potassium

iodate(V) and 10 cm3 of aqueous potassium iodide. There is an excess of each of these reagents.

• Place the flask on a white tile. • Titrate the liberated iodine with FA 2. • During the titration the colour of the iodine in the solution will fade from red-brown

to orange to yellow. The end-point occurs when the solution just goes colourless with the addition of a single drop of FA 2.

• You should perform a rough titration. In the space below record your burette readings for this rough titration.

The rough titre is ................................. cm3

• Carry out as many accurate titrations as you think necessary to obtain consistent results.

• Record in a suitable form below all of your burette readings and the volume of FA 2 added in each accurate titration.

• Make certain any recorded results show the precision of your practical work.

[7]

I

II

III

IV

V

VI

VII



3


ForExaminer’s

Use

(b) From your titration results obtain a suitable value to be used in your calculation.Show clearly how you have obtained this value.

25.0 cm3 of FA 1 require .............. cm3 of FA 2. [1]

Calculations

Show your working and appropriate significant figures in the final answer to each step of your calculations.

(c) (i) Calculate the concentration, in mol dm–3, of the sodium thiosulfate in FA 2. FA 2 contai ns 15.0 g dm–3 Na2S2O3.5H2O. [Ar: H, 1.0; O, 16.0; Na, 23.0; S, 32.1]

The concentration of sodium thiosulfate in FA 2 is ............................ mol dm–3.

(ii) Calculate how many moles of Na2S2O3 are contained in the volume of FA 2 recorded in (b).

.............. mol of Na2S2O3

(iii) Calculate how many moles of iodine, I2 reacted with the Na2S2O3 in (ii).

2Na2S2O3(aq) + I2(aq) Na2S4O6(aq) + 2NaI(aq)

............................ mol of iodine reacted with the sodium thiosulfate.

(iv) Calculate how many moles of hydrochloric acid, HCl, reacted with an excess of potassium iodate(V) and an excess of potassium iodide to produce the amount of iodine calculated in (iii).


............................ mol of HCl produced the amount of iodine calculated in (iii).

I

II

III

IV

V



4

9701/31/O/N/10© UCLES 2010

ForExaminer’s

Use

(v) Calculate the concentration, in mol dm–3, of HCl in FA 1.

The concentration of HCl in FA 1 is ....................... mol dm–3. [5]

(d)

Each reading with a burette has a maximum error of ±0.05 cm3.Grade B volumetric (bulb) pipettes are calibrated to ±0.06 cm3.

(i) Calculate the maximum error in the volume run from the burette recorded in any titration.

The maximum error is ............................... cm3.

(ii) Express the maximum error calculated in (i) as a percentage error for the volume calculated in (b).

The maximum error is .................................. %.

(iii) Calculate the percentage error when 25.0 cm3 of FA 1 was pipetted into the conical flask.

The error was .................................. %.[2]

[Total: 15]



5


BLANK PAGE



6

9701/31/O/N/10© UCLES 2010

ForExaminer’s

Use

2 FA 3 is powdered basic copper(II) carbonate, a hydrated mixture of copper(II) carbonate and copper(II) hydroxide.

The approximate formula for the basic carbonate is CuCO3.Cu(OH)2.H2O.

When heated, basic copper(II) carbonate decomposes.

CuCO3.Cu(OH)2.H2O(s) 2CuO(s) + CO2(g) + 2H2O(g)

You are to determine the change in mass as the solid is heated and decomposed.


• Record all weighings in an appropriate form in the space below. • Weigh and record the mass of an empty boiling-tube. • Tip the contents of the tube labelled FA 3 into the weighed boiling-tube. Reweigh

and record the total mass of the boiling-tube and FA 3. • Heat FA 3 in the boiling-tube very gently until the vigorous decomposition of

the copper carbonate has stopped; then heat more strongly for 1 to 2 minutes.Take care not to lose any solid from the tube during the initial heating.

• Warm the upper parts of the boiling-tube to evaporate any water that may have condensed while heating the carbonate.

• Place the hot tube on a heat-proof mat and leave to cool. • You are advised to continue with part (d) of this question or to start another

question while the tube cools. • When cool, reweigh the boiling-tube and the residual copper(II) oxide. • Reheat, cool and reweigh the tube until you are satisfied decomposition is

complete.

Results

In an appropriate form, in the space below, record all of your balance readings, the mass of basic copper(II) carbonate and the mass of residual copper oxide.

[6]

I

II

III

IV

V

VI



7


ForExaminer’s

Use

Calculations

(b) Calculate the loss in mass during the experiment as a percentage of the mass of solid heated.

[1]

(c) The theoretical loss in mass is 33.5%.

The proportions of CuCO3 and Cu(OH)2 in the basic carbonate can vary from the 1:1 ratio given in the formula.

Make use of the following information to account for the difference between the value you have calculated in (b) and the theoretical percentage loss in mass.

1 mol CuCO3(s) 1 mol C O2(g)1 mol Cu(OH)2(s) 1 mol H 2O(g)

Assume that 1 mol of any sample of the solid basic carbonate contains 1 mol H2O.

[Mr: CO2, 44.0; H2O, 18.0]

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Add to the diagram below additional standard laboratory apparatus that would enable you to collect and measure the volume of carbon dioxide evolved in the experiment.

Ensure that your apparatus does not also collect and measure any of the water vapour evolved.

heat [2]

[Total: 10]



8

9701/31/O/N/10© UCLES 2010

ForExaminer’s

Use

3 FA 4, FA 5, FA 6 and FA 7 are aqueous solutions each containing one of the ions Al 3+, Mg2+, Pb2+, Zn2+.

You will carry out the following tests on each of the solutions.






You should rinse and reuse test-tubes where possible.

testobservations

FA 4 FA 5 FA 6 FA 7

(i) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous sodium hydroxide.Swirl the tube, then

add a further 2 cm depth of aqueous sodium hydroxide.

(ii) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous ammonia.Swirl the tube, then

add a further 2 cm depth of aqueous ammonia.

(iii) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous potassium iodide.

[4]

I

II

III

IV



9


ForExaminer’s

Use

(b) Use the Qualitative Analysis Notes on page 11 to identify the cation present in each of the solutions.

Complete the table below to identify each ion and to give supporting evidence from your observations.

solution cation supporting evidence

FA 4

FA 5

FA 6

FA 7

[4]

Do not carry out the following test.

(c) Use the Qualitative Analysis Notes on pages 11 and 12 to select a further reagent that could be used to confirm the presence of Pb2+ in one of the solutions FA 4, FA 5, FA 6 and FA 7.

The reagent is ........................................................................................................... . [1]

I

II

III

IV



10

9701/31/O/N/10© UCLES 2010

ForExaminer’s

Use

(d) FA 8 contains aqueous copper(II) ions. Carry out the following tests and make careful observations of all that happens in each

experiment.

test observations

(i) To 2 cm depth of FA 8 in a boiling-tube add 1 spatula measure of zinc metal powder.

Leave to stand for 1 minute, then

add 2 cm depth of distilled water and leave to stand for a further 2 minutes.

(ii) To 1 cm depth of FA 8 in a test-tube add 1 cm depth of concentrated hydrochloric acid.(Care: corrosive)Retain the mixture for use in (iii).

(iii) Using a dropping pipette transfer 1 cm depth of the solution in (ii) into another test-tube.

Add 1 cm depth of water and shake the tube.

[5]

(e) From your observations in (d)(i) complete the equation below:

Cu2+(aq) + Zn(s) [1]

[Total: 15]

I

II

III

IV

V



11



Key: [ ppt. = precipitate ]


ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




12

9701/31/O/N/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)


sulfite,

SO32– (aq)



3 Tests for gases













DC (NH/SW) 35386© UCLES 2010 [Turn over







*7382672438*

CHEMISTRY 9701/33


2 hours



Session

Laboratory


1

2

3

Total



2

9701/33/O/N/10© UCLES 2010

ForExaminer’s

Use


1 You are to determine the concentration of hydrochloric acid, which supplies the H+ ions in the following reaction.


In the presence of an excess of IO3– ions and an excess of I– ions, the amount of I2 liberated

is directly proportional to the amount of H+ ions present and can be determined by titration with sodium thiosulfate, Na2S2O3.

You are provided with the following reactants.

FA 1 hydrochloric acid FA 2 contai ning 15.0 g dm–3 sodium thiosulfate, Na2S2O3.5H2O aqueous potassium iodate(V), KIO3 aqueous potassium iodide, KI

(a) Method

• Fill a burette with FA 2. • Pipette 25.0 cm3 of FA 1 into the conical flask. • Use a 25 cm3 measuring cylinder to add to the flask 10 cm3 of aqueous potassium

iodate(V) and 10 cm3 of aqueous potassium iodide. There is an excess of each of these reagents.

• Place the flask on a white tile. • Titrate the liberated iodine with FA 2. • During the titration the colour of the iodine in the solution will fade from red-brown

to orange to yellow. The end-point occurs when the solution just goes colourless with the addition of a single drop of FA 2.

• You should perform a rough titration. In the space below record your burette readings for this rough titration.

The rough titre is ................................. cm3


• Record in a suitable form below all of your burette readings and the volume of FA 2 added in each accurate titration.


[7]

I

II

III

IV

V

VI

VII



3


ForExaminer’s

Use

(b) From your titration results obtain a suitable value to be used in your calculation.Show clearly how you have obtained this value.

25.0 cm3 of FA 1 require .............. cm3 of FA 2. [1]

Calculations


(c) (i) Calculate the concentration, in mol dm–3, of the sodium thiosulfate in FA 2. FA 2 contai ns 15.0 g dm–3 Na2S2O3.5H2O. [Ar: H, 1.0; O, 16.0; Na, 23.0; S, 32.1]

The concentration of sodium thiosulfate in FA 2 is ............................ mol dm–3.

(ii) Calculate how many moles of Na2S2O3 are contained in the volume of FA 2 recorded in (b).

.............. mol of Na2S2O3

(iii) Calculate how many moles of iodine, I2 reacted with the Na2S2O3 in (ii).

2Na2S2O3(aq) + I2(aq) Na2S4O6(aq) + 2NaI(aq)

............................ mol of iodine reacted with the sodium thiosulfate.

(iv) Calculate how many moles of hydrochloric acid, HCl, reacted with an excess of potassium iodate(V) and an excess of potassium iodide to produce the amount of iodine calculated in (iii).


............................ mol of HCl produced the amount of iodine calculated in (iii).

I

II

III

IV

V



4

9701/33/O/N/10© UCLES 2010

ForExaminer’s

Use

(v) Calculate the concentration, in mol dm–3, of HCl in FA 1.

The concentration of HCl in FA 1 is ....................... mol dm–3. [5]

(d)

Each reading with a burette has a maximum error of ±0.05 cm3.Grade B volumetric (bulb) pipettes are calibrated to ±0.06 cm3.

(i) Calculate the maximum error in the volume run from the burette recorded in any titration.

The maximum error is ............................... cm3.

(ii) Express the maximum error calculated in (i) as a percentage error for the volume calculated in (b).

The maximum error is .................................. %.

(iii) Calculate the percentage error when 25.0 cm3 of FA 1 was pipetted into the conical flask.

The error was .................................. %.[2]

[Total: 15]



5


BLANK PAGE



6

9701/33/O/N/10© UCLES 2010

ForExaminer’s

Use

2 FA 3 is powdered basic copper(II) carbonate, a hydrated mixture of copper(II) carbonate and copper(II) hydroxide.

The approximate formula for the basic carbonate is CuCO3.Cu(OH)2.H2O.

When heated, basic copper(II) carbonate decomposes.

CuCO3.Cu(OH)2.H2O(s) 2CuO(s) + CO2(g) + 2H2O(g)

You are to determine the change in mass as the solid is heated and decomposed.


• Record all weighings in an appropriate form in the space below. • Weigh and record the mass of an empty boiling-tube. • Tip the contents of the tube labelled FA 3 into the weighed boiling-tube. Reweigh

and record the total mass of the boiling-tube and FA 3. • Heat FA 3 in the boiling-tube very gently until the vigorous decomposition of

the copper carbonate has stopped; then heat more strongly for 1 to 2 minutes.Take care not to lose any solid from the tube during the initial heating.

• Warm the upper parts of the boiling-tube to evaporate any water that may have condensed while heating the carbonate.

• Place the hot tube on a heat-proof mat and leave to cool. • You are advised to continue with part (d) of this question or to start another

question while the tube cools. • When cool, reweigh the boiling-tube and the residual copper(II) oxide. • Reheat, cool and reweigh the tube until you are satisfied decomposition is

complete.

Results

In an appropriate form, in the space below, record all of your balance readings, the mass of basic copper(II) carbonate and the mass of residual copper oxide.

[6]

I

II

III

IV

V

VI



7


ForExaminer’s

Use

Calculations

(b) Calculate the loss in mass during the experiment as a percentage of the mass of solid heated.

[1]

(c) The theoretical loss in mass is 33.5%.

The proportions of CuCO3 and Cu(OH)2 in the basic carbonate can vary from the 1:1 ratio given in the formula.

Make use of the following information to account for the difference between the value you have calculated in (b) and the theoretical percentage loss in mass.

1 mol CuCO3(s) 1 mol C O2(g)1 mol Cu(OH)2(s) 1 mol H 2O(g)

Assume that 1 mol of any sample of the solid basic carbonate contains 1 mol H2O.

[Mr: CO2, 44.0; H2O, 18.0]

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

(d) Add to the diagram below additional standard laboratory apparatus that would enable you to collect and measure the volume of carbon dioxide evolved in the experiment.

Ensure that your apparatus does not also collect and measure any of the water vapour evolved.

heat [2]

[Total: 10]



8

9701/33/O/N/10© UCLES 2010

ForExaminer’s

Use

3 FA 4, FA 5, FA 6 and FA 7 are aqueous solutions each containing one of the ions Al 3+, Mg2+, Pb2+, Zn2+.







You should rinse and reuse test-tubes where possible.

testobservations

FA 4 FA 5 FA 6 FA 7



(ii) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous ammonia.Swirl the tube, then


(iii) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous potassium iodide.

[4]

I

II

III

IV



9


ForExaminer’s

Use




FA 4

FA 5

FA 6

FA 7

[4]

Do not carry out the following test.

(c) Use the Qualitative Analysis Notes on pages 11 and 12 to select a further reagent that could be used to confirm the presence of Pb2+ in one of the solutions FA 4, FA 5, FA 6 and FA 7.

The reagent is ........................................................................................................... . [1]

I

II

III

IV



10

9701/33/O/N/10© UCLES 2010

ForExaminer’s

Use

(d) FA 8 contains aqueous copper(II) ions. Carry out the following tests and make careful observations of all that happens in each

experiment.

test observations

(i) To 2 cm depth of FA 8 in a boiling-tube add 1 spatula measure of zinc metal powder.

Leave to stand for 1 minute, then

add 2 cm depth of distilled water and leave to stand for a further 2 minutes.

(ii) To 1 cm depth of FA 8 in a test-tube add 1 cm depth of concentrated hydrochloric acid.(Care: corrosive)Retain the mixture for use in (iii).

(iii) Using a dropping pipette transfer 1 cm depth of the solution in (ii) into another test-tube.

Add 1 cm depth of water and shake the tube.

[5]

(e) From your observations in (d)(i) complete the equation below:

Cu2+(aq) + Zn(s) [1]

[Total: 15]

I

II

III

IV

V



11





ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




12

9701/33/O/N/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),CrO4

2– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)


sulfite,

SO32– (aq)



3 Tests for gases













DC (CW) 28188/3© UCLES 2010 [Turn over

*1863307025*







CHEMISTRY 9701/34


2 hours



Session

Laboratory


1

2

3

Total



2

9701/34/O/N/10© UCLES 2010

ForExaminer’s

Use


1 FB 1 is an aqueous solution containing 21.50 g dm–3 of a mixture of iron(II) sulfate, FeSO4 and iron(III) sulfate, Fe2(SO4)3.

FB 2 is an aqueous solution containing 2.00 g dm–3 potassium manganate(VII), KMnO4.

In the presence of acid, the iron(II) sulfate is oxidised by potassium manganate(VII).

2KMnO4(aq) + 8H2SO4(aq) + 10FeSO4(aq) 5Fe2(SO4)3(aq) + 2MnSO4(aq) + K2SO4(aq) + 8H2O(l)

(a) Method

• Fill a burette with FB 2. • Pipette 25.0 cm3 of FB 1 into the conical flask. • Use a 25 cm3 measuring cylinder to add 10 cm3 of dilute sulfuric acid to the flask. • Place the flask on a white tile. • Carefully titrate with FB 2 until the first permanent pink colour is obtained.

You should perform a rough titration. In the space below record your burette readings for this rough titration.

The rough titre is ............................ cm3.


• Record in a suitable form below all of your burette readings and the volume of FB 2 added in each accurate titration.


[7]

I

II

III

IV

V

VI

VII



3


ForExaminer’s

Use

(b) From your accurate titration results obtain a suitable value to be used in your calculation. Show clearly how you have obtained this value.

25.0 cm3 of FB 1 required .............. cm3 of FB 2. [1]

Calculations


(c) (i) Calculate the concentration, in mol dm–3, of the potassium manganate(VII) in FB 2.

FB 2 contai ns 2.00 g dm–3 KMnO4. [Ar: O, 16.0; K, 39.1; Mn, 54.9]

The concentration of potassium manganate(VII) in FB 2 is ............................ mol dm–3.

(ii) Calculate how many moles of KMnO4 were present in the volume calculated in (b).

.................... mol of KMnO4.

(iii) Calculate how many moles of iron(II) sulfate, FeSO4, reacted with the potassium manganate(VII) in (ii).

2KMnO4(aq) + 8H2SO4(aq) + 10FeSO4(aq) 5Fe2(SO4)3(aq) + 2MnSO4(aq) + K2SO4(aq) + 8H2O(l)

............................ mol of FeSO4 reacted with the potassium manganate(VII).

I

II

III

IV

V



4

9701/34/O/N/10© UCLES 2010

ForExaminer’s

Use

(iv) Calculate the concentration, in mol dm–3 of FeSO4 in FB 1.

The concentration of FeSO4 in FB 1 is ....................... mol dm–3.

(v) Calculate the concentration, in g dm–3, of FeSO4 in FB 1. [Ar: O, 16.0; S, 32.1; Fe, 55.8]

FB 1 contains ..................... g dm–3 of FeSO4.

(vi) FB 1 is an aqueous solution containing 21.50 g dm–3 of FeSO4 and Fe2(SO4)3. Calculate the percentage, by mass, of FeSO4 in this mixture.

The mixture contains ....................... % FeSO4. [5]

[Total: 13]



5


BLANK PAGE



6

9701/34/O/N/10© UCLES 2010

ForExaminer’s

Use

2 FB 3 is a mixture containing anhydrous sodium carbonate, Na2CO3, and sodium hydrogencarbonate, NaHCO3.

When heated, sodium hydrogencarbonate decomposes.

2NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g)

Anhydrous sodium carbonate does not decompose when heated.

You are to determine if sodium hydrogencarbonate is the major component, by mass, of the mixture in FB 3.


• Weigh and record the mass of an empty boiling-tube. • Tip the contents of the tube labelled FB 3 into the weighed boiling-tube. Reweigh

and record the mass of the boiling-tube and FB 3. • Gently heat the FB 3 in the boiling-tube for 2 minutes then heat strongly for a further

2 minutes. Take care not to lose any solid from the tube during heating. • Warm the upper parts of the boiling-tube to evaporate any water that may have

condensed while heating the solid. • Place the hot tube on a heat-proof mat and leave to cool. • You are advised to continue with part (d) of this question or to start another

question while the tube cools. • When cool, reweigh the boiling-tube and the residual sodium carbonate. • Reheat, cool and reweigh the tube until you are satisfied decomposition is

complete.

Results

In an appropriate form, in the space below, record all of your balance readings, the mass of FB 3 heated, the mass of residual sodium carbonate and the mass loss on heating.

[6]

I

II

III

IV

V

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7


ForExaminer’s

Use

Calculations

Do not use your experimental results in part (i)

(b) (i) Use the equation for the decomposition of NaHCO3 on heating to

calculate the theoretical ratio mass of NaHCO3

mass loss on heating.

2NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g)

[Mr: NaHCO3, 84.0; CO2, 44.0; H2O, 18.0]

theoretical ratio = .......................................

(ii) Use the following expression to calculate the mass of NaHCO3 in the sample of FB 3 that was heated.

theoretical ratio from b(i) × experimental mass loss from (a)

mass of NaHCO3 = .................................... g

(iii) Tick the appropriate box in the table below.

NaHCO3 is the major component, by mass, in FB 3

NaHCO3 is not the major component, by mass, in FB 3

Justify your answer with supporting evidence.

..................................................................................................................................

.................................................................................................................................. [2]



8

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ForExaminer’s

Use

(c) Do not carry out your suggestions.

Suggest two ways in which you could show that sodium carbonate does not decompose on heating.

(i) ....................................................................................................................................

.........................................................................................................................................

(ii) ...................................................................................................................................

..................................................................................................................................... [2]

(d) A student is asked to weigh, with maximum precision, a solid.

The three balances available are:

balance A, reading to 1 decimal place, balance B, reading to 2 decimal places, balance C, reading to 3 decimal places.

The smallest division on a burette is 0.1 cm3.The maximum error in a single burette reading is ±0.05 cm3

Balance readings can be treated in the same way.

Complete the following table.

balancemaximum error for a

single balance reading / g

maximum % error when weighing:

A ± 9.0 g of solid =

B ± 4.00 g of solid =

C ± 0.500 g of solid =

[2]

[Total: 12]



9


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10

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ForExaminer’s

Use

3 FB 4, FB 5, FB 6 and FB 7 are aqueous solutions each containing one of the ions Al 3+, NH4

+, Mg2+, Mn2+.





You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling-tube MUST be used.


testobservations

FB 4 FB 5 FB 6 FB 7



In tests (ii) and (iii) put a cross in any boxes where the test is not carried out.

(ii) If a precipitateremains at the endof test (i) leave the test-tube and contents to stand for a few minutes.

(iii) If no precipitate formed at all in test (i) tip the contents of the tube into a boiling-tube and warm gently.Care: heated solutions containing sodium hydroxide are liable to be ejected from the tube.



11


ForExaminer’s

Usetestobservations

FB 4 FB 5 FB 6 FB 7

(iv) To 1 cm depth of solution in a test-tube add 1 cm depth of aqueous ammonia.Swirl the tube, then


[6]




FB 4

FB 5

FB 6

FB 7

[4]

Rinse and re-use test-tubes where possible.

I

II

III

IV

V

VI

I

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ForExaminer’s

Use

(c) Carry out the following tests on the solution you have identified as containing Al 3+ ions and record your observations in the spaces provided.

observation

(i) Add aqueous sodium iodide

(ii) Add dilute sulfuric acid

Explain how your results confirm the presence of Al 3+ and eliminate any other ion.

.........................................................................................................................................

..................................................................................................................................... [1]

(d) What other cation listed in the Qualitative Analysis Notes on page 13 would give similar results to Al 3+ in (a)?

..................................................................................................................................... [1]

(e) Carry out the following tests and make careful observations of all that happens in each experiment. Complete the table.

test observations

(i) To 1 cm depth of aqueous silver nitrate in a test-tube add 1 cm depth of aqueous sodium chloride.Keep the tube for comparison with the observations in test (ii).

(ii) Repeat test (i).To 1 cm depth of aqueous silver nitrate in a test-tube add 1 cm depth of aqueous sodium chloride,then

Do not repeat your observations from test (i)

add 1 cm depth of aqueous sodium iodide and shake the tube.

[2]

(f) Suggest an explanation for your observations when aqueous sodium iodide is added in test (e)(ii).

.........................................................................................................................................

.........................................................................................................................................

..................................................................................................................................... [1]

[Total: 15]



13





ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




14

9701/34/O/N/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)


sulfite,

SO32– (aq)



3 Tests for gases










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DC (NF) 28264/3© UCLES 2010 [Turn over

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONSGeneral Certificate of EducationAdvanced Subsidiary Level and Advanced Level

*4827396477*

CHEMISTRY 9701/35


2 hours








Session

Laboratory


1

2

3

Total



2

9701/35/O/N/10© UCLES 2010

ForExaminer’s

Use

1 FA 1 is an aqueous solution of hydrochloric acid, HCl. FA 2 is aqueous sodium hydroxide containing 10.00 g dm–3 NaOH.

You are to determine the concentration, in mol dm–3, of the hydrochloric acid in FA 1.

(a) Method

Fill a burette with • FA 2.Pipette 10.0 cm • 3 of FA 1 into a conical flask.Add to the flask a few drops of the acid-base indicator provided. •Place the flask on a white tile. •Titrate the acid in the flask with • FA 2.


The rough titre is .............................................. cm3.

Carry out as many accurate titrations as you think necessary to obtain consistent •results.Record in a suitable form below all of your burette readings and the volume of • FA 2 added in each accurate titration.Make certain any recorded results show the precision of your practical work. •

[7]

(b) From your titration results obtain a suitable value to be used in your calculation. Show clearly how you have obtained this value.

10.0 cm3 of FA 1 required ................................. cm3 of FA 2. [1]

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ForExaminer’s

Use

Calculations


(c) (i) Calculate the concentration, in mol dm–3, of the sodium hydroxide in FA 2. FA 2 contai ns 10.00 g dm–3 NaOH. [Ar: H, 1.0; O, 16.0; Na, 23.0]

The concentration of sodium hydroxide in FA 2 is ...................................... mol dm–3.

(ii) Calculate how many moles of sodium hydroxide are contained in the volume recorded in (b).

................................................................. mol of NaOH.

(iii) Deduce how many moles of hydrochloric acid were pipetted into the conical flask and calculate the concentration, in mol dm–3, of the hydrochloric acid in FA 1.

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

The concentration of the hydrochloric acid in FA 1 is ...................................... mol dm–3. [2]

[Total: 10]

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5


ForExaminer’s

Use

2 FA 3 is crushed impure calcium carbonate, CaCO3. FA 4 i s 0.500 mol dm–3 hydrochloric acid FA 5 i s 0.280 mol dm–3 sodium hydroxide.

You are to determine the percentage purity of calcium carbonate by dissolving a measured mass of FA 3 in a known volume of hydrochloric acid, which is in excess.

The hydrochloric acid remaining after all the calcium carbonate has dissolved can be determined by titration with aqueous sodium hydroxide, FA 4.

You may assume that any impurity present in the calcium carbonate does not react with hydrochloric acid.


Weigh and record the mass of an empty boiling-tube. •Add to the boiling-tube between 2.60 g and 2.80 g of • FA 3.Reweigh the tube and its contents. •In part • (b) of the method you will tip the FA 3 into hydrochloric acid, then re-weigh the tube and any residual FA 3.

In the space below record, in an appropriate form, all of the balance readings and the mass of FA 3 used in the experiment.

[2]

(b) Method – Read through the instructions before starting any practical work.

Pour approximately 150 cm • 3 of FA 4 into a 250 cm3 beaker.Add, a little at a time with constant stirring, the weighed • FA 3 to the acid in the beaker.After each small addition stir until the effervescence has ceased and all the solid •has dissolved.Reweigh the tube and any residual • FA 3. Record the mass in (a).Transfer the solution in the beaker to the 250 cm • 3 graduated (volumetric) flask labelled FA 6.Rinse the beaker several times with • a small amount of FA 4 and add the rinsings to the graduated flask.Make up the solution to the 250 cm • 3 mark by adding FA 4, not water.Shake the flask to obtain a uniform solution. •

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ForExaminer’s

Use

Titration

Fill a burette with • FA 5.Pipette 25.0 cm • 3 of FA 6 from the graduated flask into a conical flask.Add to the flask a few drops of the acid-base indicator provided. •Place the flask on a white tile. •Titrate the acid in the flask with • FA 5.


The rough titre is .............................................. cm3.

Carry out as many accurate titrations as you think necessary to obtain consistent •results.Record in a suitable form below all of your burette readings and the volume of • FA 5 added in each titration.Make certain any recorded results show the precision of your practical work. •

[2]

(c) From your titration results obtain a suitable value to be used in your calculation. Show clearly how you have obtained this value.

25.0 cm3 of FA 6 required ................................. cm3 of FA 5.

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ForExaminer’s

Use

(d) Calculations


Remember – FA 4 i s 0.500 mol dm–3 hydrochloric acidFA 5 i s 0.280 mol dm–3 sodium hydroxide.

(i) Calculate how many moles of sodium hydroxide are contained in the volume recorded in (c).

................................. mol of NaOH

(ii) Deduce how many moles of hydrochloric acid reacted with the sodium hydroxide in (i) and calculate how many moles of hydrochloric acid were present in the 250 cm3 graduated flask labelled FA 6.

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

........................ mol of HCl were present in the graduated flask.

(iii) Calculate how many moles of hydrochloric acid were present in 250 cm3 of FA 4.

250 cm3 of FA 4 contained ....................................... mol HCl.

(iv) Calculate the following.

(answer to (d)(iii) – answer to (d)(ii))

This is the amount of hydrochloric acid that reacted with the calcium carbonate in the weighed sample of FA 3.

............... mol of HCl reacted with the calcium carbonate in ............... g FA 3.

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ForExaminer’s

Use

(v) Use your answer to (iv) to calculate the mass of calcium carbonate that reacted with hydrochloric acid.

This is the mass of pure CaCO3 in the weighed sample of FA 3.

CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l)

[Ar: Ca, 40.0; C, 12.0; O, 16.0]

The weighed sample of FA 3 contains .................................. g of CaCO3.

(vi) Calculate the percentage of calcium carbonate, CaCO3, in FA 3 by evaluating the following expression.

mass of CaCO3 from (d)(v)mass of FA 3 used, from (a) × 100

Complete your evaluation even if your answer is greater than 100%

FA 3 contains ................... % calcium carbonate. [5]

(e) 6.25 g of pure calcium carbonate are required to neutralise all the hydrochloric acid in 250 cm3 of FA 4.

You were instructed to measure a mass between 2.60 g and 2.80 g of FA 3 in this experiment.

What difficulties might you encounter if you used a mass of about 5.50 g of FA 3 in this experiment?

..........................................................................................................................................

..........................................................................................................................................

.......................................................................................................................................... [1]

III

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ForExaminer’s

Use

(f) (i) Complete the following table.

The balance used in the experiment displays the mass to ........................ decimal places.

The maximum error in a single balance reading is ± ..................... g.

The maximum error in measuring the mass of FA 3 is ± ..................... g.

(ii) Calculate the maximum percentage error in the mass of FA 3 measured in (a).

The maximum error in the mass of FA 3 is ................................................. %. [2]

(g) (i) The percentage of calcium carbonate in the weighed sample of FA 3 can also be found by investigating the thermal decomposition of the compound into calcium oxide and carbon dioxide.

Write a balanced equation, including state symbols, for this thermal decomposition.

(ii) Briefly outline the key measurements to be made in order to find the percentage of calcium carbonate in FA 3 by this method.

1. ..............................................................................................................................

2. ..............................................................................................................................

3. ..............................................................................................................................

4. ..............................................................................................................................

5. ..............................................................................................................................

6. ..............................................................................................................................

(You do not have to use all of the numbered steps in your answer) [2]

[Total: 14]



10

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ForExaminer’s

Use

3 FA 7, FA 8 and FA 9 are aqueous solutions, each containing one cation and one anion from those listed on pages 13 and 14 in the Qualitative Analysis Notes.

At each stage of any test you are to record details of the following.colour changes seen •the formation of any precipitate •the solubility of such precipitates in an excess of the reagent added •


You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling-tube MUST be used. Rinse and reuse test-tubes wherever possible.

(a) Use aqueous sodium hydroxide and aqueous ammonia, in separate tests, to identify the cation present in FA 7, FA 8 and FA 9.

Present your results for each of the solutions in a suitable form below.

Conclusion

Complete the following table.


FA 7

FA 8

FA 9

[6]

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Use

(b) (i) FA 7, FA 8 and FA 9 each contain a single anion which may be Cl –, I– or SO42–.

Suggest a reagent that would enable you to identify any solutions containing SO42–.

Reagent ....................................................................................................................

Use this reagent to test each of the solutions. Record your observations in the table below. Indicate, with a tick in the final column, any solution containing SO4

2–.

solution observation SO42– present

FA 7

FA 8

FA 9

(ii) Select a further reagent that will enable you to identify the halide ion present in any remaining solution(s).

Reagent ……………………………………………………….………………………..

Use this reagent to test the remaining solution(s). Record your observations and the identity of the halide in a suitable form in the

space below.

[5]

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ForExaminer’s

Use

(c) FA 10 is a white crystalline solid which turns into another white solid, FA 11, when heated strongly.

Carry out the tests on FA 10 and FA 11 in the table below. Observe carefully at each stage and record all of your observations in the table.

test observations

(i) Place 1 spatula measure of FA 10 in a hard glass test-tube.

Heat the solid very strongly until no further change is seen.

(ii) Place 1 small spatula measure of FA 11 in a test-tube and add 1 cm depth of dilute hydrochloric acid.

As soon as you have completed your observation in (ii), fill the test-tube with water.

[5]

[Total: 16]

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13





ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al 3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,





grey-green ppt.

insoluble in excess

copper(II),Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess



insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




14

9701/35/O/N/10© UCLES 2010


ion reaction

carbonate,

CO32–


chromate(VI),

CrO42–(aq)




chloride,

Cl –(aq)



bromide,

Br–(aq)



iodide,

I–(aq)



nitrate,

NO3–(aq)


nitrite,

NO2–(aq)



sulfate,

SO42–(aq)


sulfite,

SO32–(aq)



3 Tests for gases



carbon dioxide, CO2 gives a white ppt. with limewater

(ppt. dissolves with excess CO2)







15

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16

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DC (LEO) 28255/3© UCLES 2010 [Turn over

*4991551712*




Answer all questions.You may lose marks if you do not show your working or if you do not useappropriate units.Use of a Data Booklet is unnecessary.



CHEMISTRY 9701/36


2 hours



Session

Laboratory


1

2

3

Total



2

9701/36/O/N/10© UCLES 2010

ForExaminer’s

Use

You must prepare Flask A and Flask B in Question 2 before starting Question 1. Shake each flask periodically during the time you spend on Question 1.

1 FB 1 i s 0.125 mol dm–3 sulfuric acid, H2SO4. FB 2 is an aqueous solution of sodium hydroxide, NaOH.

You are to determine the concentration, in mol dm–3, of the sodium hydroxide in FB 2.

(a) Method

• Fill a burette with FB 1. • Run between 45.50 cm3 and 46.50 cm3 of FB 1 from the burette into the 250 cm3

graduated (volumetric) flask, labelled FB 3. • Make up to the mark with distilled water. • Shake the flask to mix the solution.

In the space below record your burette readings and the volume of FB 1 added to the graduated flask.

You are reminded to shake Flask A and Flask B periodically.

Titration

• Fill a second burette with FB 2. • Pipette 25.0 cm3 of FB 3, the diluted acid, into a conical flask. • Add to the flask a few drops of phenolphthalein indicator. • Place the flask on a white tile. • Titrate the acid in the flask with FB 2. At the end-point a “permanent” pink colour will remain in the solution. • Note: The “permanent” pink colour will fade over several minutes as carbon dioxide

is absorbed from the atmosphere.


The rough titre is ......................... cm3.

• Carry out as many accurate titrations as you think necessary to obtain consistent results

• Record in a suitable form on page 3 all of your burette readings and the volume of FB 2 added in each accurate titration.


You will require the burette containing FB 2 for Question 2.



3


ForExaminer’s

Use

[7]

(b) From your accurate titration results obtain a suitable value to be used in your calculation.Show clearly how you have obtained this value.

25.0 cm3 of FB 3 required ....................... cm3 of FB 2. [1]

Calculations Show your working and appropriate significant figures in the final answer to each step

of your calculations.

(c) (i) Calculate how many moles of H2SO4 in FB 1 were run from the burette into the 250 cm3 graduated, (volumetric) flask.

............................ mol of H2SO4 were run from the burette into the graduated flask.

(ii) Calculate how many moles of H2SO4 in FB 3 were pipetted from the graduated flask into the conical flask in each titration.

............................ mol of H2SO4 were pipetted into the conical flask.

(iii) Calculate how many moles of NaOH reacted with the H2SO4 in (ii).

H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l)

The H2SO4 in the titration flask reacted with ............................ mol of NaOH.

I

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V

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4

9701/36/O/N/10© UCLES 2010

ForExaminer’s

Use

(iv) Calculate the concentration, in mol dm–3, of NaOH in FB 2.

The concentration of NaOH in FB 2 is …………………. mol dm–3. [5]

(d) The individual error in any burette reading is ±0.05 cm3. Two students, A and B, record identical burette readings.

final burette reading 25.60 cm3

initial burette reading 1.35 cm3

volume added 24.25 cm3

Explain the following.

(i) The initial burette reading made by student A was 0.05 cm3 greater than the true value but the volume added was exactly 24.25 cm3.

..................................................................................................................................

..................................................................................................................................

(ii) The initial burette reading made by student B was 0.05 cm3 less than the true value and the actual volume added was exactly 24.15 cm3.

..................................................................................................................................

.................................................................................................................................. [2]

(e) In the instructions for the experiment you were told that the “permanent” pink colour at the end-point would fade over a few minutes as carbon dioxide is absorbed from the atmosphere.

(i) Explain why absorption of carbon dioxide at the end-point would reverse the indicator colour change seen in the titration.

..................................................................................................................................

..................................................................................................................................

(ii) Suggest a modification to the titration method, using the same indicator, that would overcome this problem.

..................................................................................................................................

.................................................................................................................................. [2]

[Total: 17]



5


ForExaminer’s

Use

2 FB 4 i s 0.050 mol dm–3 sodium hydroxide solution. FB 5 is 0.200 mol dm–3 propanoic acid, C2H5CO2H. FB 6 is an organic liquid that does not mix with water.

Propanoic acid dissolves both in water and in the organic layer, FB 6. When an aqueous solution of the acid is shaken with FB 6, some of the acid transfers to the

organic layer. The amount of acid remaining in the aqueous layer can be determined by titration with

aqueous sodium hydroxide.

Preparation of the mixture in Flask A and in Flask B.

Flask A • Use a measuring cylinder to place 50 cm3 of FB 5 into the stoppered flask

labelled Flask A. • Use a second measuring cylinder to add to the flask 40 cm3 of FB 6, the organic

liquid. • Replace the stopper in the flask.

Flask B • Use the first measuring cylinder to place 50 cm3 of FB 5 into the stoppered flask

labelled Flask B. • Use the second measuring cylinder to add to the flask 60 cm3 of FB 6, the

organic liquid. • Replace the stopper in the flask.

• Shake both flasks vigorously for about 1 minute. • Leave the flasks on the workbench and start Question 1. • Shake the flasks for a further minute at intervals during the course of your work

on another question.

(a) Titrations

For each flask follow the same procedure.

• Empty the burette containing FB 2. • Rinse the burette thoroughly with FB 4. • Fill the burette with FB 4. • Ensure the two layers have separated – this should take no longer than 1 minute

after shaking the flask. • Pipette 10.0 cm3 of the lower (aqueous) layer into a conical flask. Attach the pipette

filler to the pipette before inserting it into the mixture, in order to close the top of the pipette to prevent any of the top (organic) layer from entering the pipette.

• Replace the stopper in the flask. • Titrate the acid in the conical flask with FB 4, using phenolphthalein indicator, as in

Question 1. • One titration will be sufficient for each experiment but take care to ensure

that no errors are made during the procedure.

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9701/36/O/N/10© UCLES 2010

ForExaminer’s

Use

Results Record, in a single table below, the burette readings and volume of FB 4 added, for

each of Flask A and Flask B.

[4]

(b) Calculations

In these calculations make use of the following.

• The concentration of NaOH in FB 4 is 0.050 mol dm–3.• 50 cm3 of 0.200 mol dm–3 propanoic acid, the volume of acid added to each

flask, contains 0.010 mol C2H5CO2H.• 1 mol C2H5CO2H reacts with 1 mol NaOH.

(i) Calculate the volume of FB 4 that contains 0.010 mol NaOH. This is the volume of FB 4 that would have reacted with the propanoic acid in the

50 cm3 of the aqueous layer, before shaking with the organic liquid.

Volume of FB 4 = ........................... cm3

(ii) For each flask, use your titration result in (a) to calculate the volume of FB 4 needed to react with the acid remaining in 50 cm3 of the aqueous layer, after shaking with the organic liquid.

Flask A Flask B

volume of FB 4 = ........................ cm3 volume of FB 4 = ........................ cm3

(iii) The amount of propanoic acid transferred to the organic layer can be represented by the following.

(answer to (i) – answer to (ii))

For each flask evaluate this expression.

Flask A (answer to (i) – answer to (ii)) = .................................... cm3

Flask B (answer to (i) – answer to (ii)) = .................................... cm3

[2]



7


ForExaminer’s

Use

(c) In which flask was most propanoic acid transferred to the organic layer?

Justify your answer.

.........................................................................................................................................

.........................................................................................................................................

......................................................................................................................................... [1]

(d) It is suggested that shaking the mixture leads to the following equilibrium being established.

C2H5CO2H(aq) C2H5CO2H(org)

Determine the equilibrium constant by evaluating the expressions in the following table.

(i) Determine the equilibrium constant by evaluating the expressions in the following table. Ignore units.

Flask A Flask B

Kc = answer (b)(iii)answer (b)(ii)

× 1.25 Kc = answer (b)(iii)answer (b)(ii)

× 0.83

Kc = ........................ Kc = ........................

(ii) Explain whether or not your results support the idea that equilibrium has been established in each flask.

..................................................................................................................................

..................................................................................................................................

.................................................................................................................................. [1]

[Total: 8]



8

9701/36/O/N/10© UCLES 2010

ForExaminer’s

Use

3 FB 7, FB 8 and FB 9 are aqueous solutions, each containing cations and anions from those listed on pages 11 and 12 in the Qualitative Analysis Notes.




You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling-tube MUST be used. Rinse and reuse test-tubes and boiling-tubes where possible.

(a) (i) One or more of the solutions FB 7, FB 8 and FB 9 are believed to contain the ammonium ion, NH4

+.

Suggest a reagent that would enable you to identify the presence of NH4+ and

describe how you would use the reagent in an appropriate test.

reagent .....................................................................................................................

test ...........................................................................................................................

..................................................................................................................................

Use this reagent to test each of the solutions. Record your observations in the table below.

solution observation

FB 7

FB 8

FB 9

I

II



9


ForExaminer’s

Use

(ii) One or more of the solutions contains the sulfate ion, SO42–.

Select reagents that would enable you to identify the presence of SO42–.

Show clearly, by describing how the reagents will be used, how you would distinguish SO4

2– from the sulfite ion, SO32–.

reagents ...................................................................................................................

test ...........................................................................................................................

Use these reagents to test each of the solutions. Record your observations in the table below.

solution observation

FB 7

FB 8

FB 9

(iii) Conclusions

The ammonium ion, NH4+, is present in ...................................................................

The sulfate ion, SO42–, is present in .........................................................................

[5]

(b) Use aqueous sodium hydroxide and aqueous ammonia in separate tests to identify any cation (apart from NH4

+) present in FB 7, FB 8 and FB 9.

Present your results for each of the solutions in a suitable form below.

[4]

III

IV

V

I

II

III

IV



10

9701/36/O/N/10© UCLES 2010

ForExaminer’s

Use

(c) Conclusion

Complete the following table. Place a cross in any box where no cation has been identified.


FB 7

FB 8

FB 9

[1]

(d) Carry out the following tests on FB 10. Observe carefully at each stage and record all of your observations in the table.

test observations

(i) Place 2 spatula measures of FB 10 in a dry, hard glass boiling-tube.

Heat the solid gently at first, then strongly until no further change is seen.

Retain the solid for use in (ii).

(ii) Tip the contents of the tube in (i) into a second boiling-tube.

Add 2 cm depth of dilute hydrochloric acid a little at a time.Warm the tube and leave to stand.

[5]

[Total: 15]

I

II

III

IV

V



11





ionreaction with

NaOH(aq) NH3(aq)

aluminium,

Al3+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

ammonium,

NH4+(aq)

no ppt.


barium,


calcium,


chromium(III),

Cr3+(aq)



grey-green ppt.

insoluble in excess

copper(II),

Cu2+(aq)

pale blue ppt.

insoluble in excess



iron(II),

Fe2+(aq)


insoluble in excess


insoluble in excess

iron(III),

Fe3+(aq)

red-brown ppt.

insoluble in excess

red-brown ppt.

insoluble in excess

lead(II),

Pb2+(aq)

white ppt.

soluble in excess

white ppt.

insoluble in excess

magnesium,

Mg2+(aq)

white ppt.

insoluble in excess

white ppt.

insoluble in excess

manganese(II),

Mn2+(aq)


insoluble in excess


insoluble in excess

zinc,

Zn2+(aq)

white ppt.

soluble in excess

white ppt.

soluble in excess




12

9701/36/O/N/10© UCLES 2010




ion reaction

carbonate,

CO32–


chromate(VI),

CrO42– (aq)




chloride,

Cl– (aq)



bromide,

Br– (aq)



iodide,

I– (aq)



nitrate,

NO3– (aq)


nitrite,

NO2– (aq)



sulfate,

SO42– (aq)


sulfite,

SO32– (aq)



3 Tests for gases










Documents

Chemistry Level) (CIE) Paper 3