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LAS Chemistry Practicals (3B) 2012 - 2013 T.A. Aoudi

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Test For gases

GAS OBSERVATIONS

Oxygen O2A colourless gas that:Relights a glowing splint

Carbon dioxide CO2

gives a white ppt. with limewater.

CO2(g) + Ca(OH)2(aq) CaCO3(s) + H2O(l)White ppt.

Sulfur dioxide SO2

A colourless acidic gas which:

Turns a filterpaper soaked with acidified potassium dichromate(VI),

K2Cr2O7from orangeto green.

3SO2 (g) + Cr2O72

(g) + 2H+ 2Cr

3++ 3SO4

2+ H2O

Orange GreenOR

decolourises a filter papersoaked with acidified purple KMnO4solution.

Hydrogen sulfide H2S smells like a rotteneggs.The gas turns lead(II) ethanoate paper from white to black.

Pb2+

+ S2

PbS

black

ammonia NH3

has a pungent orchoking smell.

The gas turns moist red litmus paperblue.

OR Produces white fumes with HClvapour

NH3(g) + HCl(g) NH4Cl(s)

Nitrogen dioxide NO2

A brown acidic gas which:

decolourises a filterpaper soaked with acidified purple KMnO4solution.

OR

gives a colourless solution in water which remains colourless uponaddition of NaOH

hydrogen H2A colouless gas which:

ignites with a pop with a lighted splint.

H2(g) + O2(g) H2O(l)

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Hydrogen chloride HCl

Gives steamy fumes when exposed to moist air;

acidic gas Turns damp blue litmus paperred. Produces white fumes withNH3(g) vapour

NH3(g) + HCl(g)

NH4Cl(s)

Hydrogen bromide HBr Gives steamy fumes when exposed to moist air;

acidic gas Turns damp blue litmus paperred. Produces white fumes withNH3(g) vapour

NH3(g) + HBr(g) NH4Br(s)

Chlorine Cl2

A pale greenchoking gas whichbleaches moist litmus paper

ORliberates orange Br2(aq)from a solutionofKBr

Cl2 + 2Br Br2(aq) + 2Cl(aq)orange

bromine Br2 Brown fumes

iodine I2 Purple fumes

Water vapourH2O

Turns anhydrous cobalt (II)chloride CoCl2 paper from

bluetopink.

Turns anhydrous copper(II) sulfate, CuSO4 from white to blue

Gases may be evolved on heating the solid

GAS POSSIBLE SOURCE

CO2Carbonates or hydrogen carbonates of metals other than Group 1.

CaCO3 heat CaO + CO2(g)

NH3 Ammonium salts NH4Br(s) heat NH3(g) + HBr(g)

O2 aloneGroup 1 nitrate [ other than Li]

KNO3(s) heat KNO2(s) + O2(g)

O2 & NO2

brown fumes

Nitrates [other than Na or K]Mg(NO3)2 (s) heat MgO(s) + 2NO2(g) + O2(g)

Hydrogen chloride

HCl(g)

Hydrated chlorides or ammonium chloride

NH4Cl(s) heat NH3 + HCl(g)

Water vapour

H2O(g)

Hydrated salt, hydrogen carbonate and otheracid salts.

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Testing gases

glowing splint

relights

Limewater

turns milky

CO2(g)

O2(g) H2(g)

Burning

splint

NH3(g)

Pop

sound

damp redlitmus turns

blue

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Test of Anions

Anion Test Test Result

CarbonateCO3

2

pH > 10

Add dilute acid

OR

Add CaCl2(aq)

orMgSO4(aq) solution

Effervescence , CO2 gas is produced.Then test for CO22H

+(aq) + CO32

CO2(g) + H2O(l)

Ca2+

+ CO32

CaCO3(s)white ppt

Hydrogencar-bonate

HCO3

PH = 8 - 9 )

Add dilute acid

OR

Add CaCl2(aq)orMgSO4(aq) solution

Effervescence , CO2 gas is produced

H+(aq) + HCO3

CO2(g) + H2O(l)

A white ppt confirms CO3

2

No ppt. in the cold ,but a white ppt onwarming confirms the presence ofHCO3

Sulfate(VI)

SO42

Add

Ba2+

(aq)i.e Ba(NO3)2then

followed by dilute HCl

OR

use Sr2+

orPb(NO3)2(aq)

White ppt.which is insolublein excessdilute strong acid ,HCl.

Ba2+

+ SO42

BaSO4(s)White ppt.

SrSO4 and PbSO4 are insoluble;

Sulfite

SO32

AddBa

2+(aq)then followed by

dilute HCl

White ppt.[solublein excess dilute strong acid to give

coloulress solution]

Ba2+

+ SO32

BaSO3(s)White ppt.

SO2 is liberated with dilute acidsBaSO3 + 2HCl BaCl2(aq) + H2O + SO2

Nitrate

NO3

Add aq. NaOH , thenaluminium foil [Devardas

alloy]

warm gently

Ammonia gas

NH3is liberated which turns dampredlitmus blue.

NH4+

+ OH

heat

NH3(g) + H2O

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NH4+

Howto testfornitratesions NO3?

Test : Add sodium hydroxide solution NaOH (aq) and aluminium foil to thesolution containing the nitrate ions.

Result : damp RED litmus turns BLUE

(alkaline) Ammonia gas is produced

The aluminium foilreduces NO3 to ammonium ion NH4

+ which reacts with

hydroxide to produce NH3(g) gas and water.

NH4+

(aq) + OH

(aq) heat NH3(g) + H2O(l)

Barium chloride ornitrate solution

BaCl2(aq) forms precipitate of insoluble barium salts with a number of anions:

Anion ppt . Addi t ion o f di lu te HCl

Colour formula

Sulfate; SO42 White BaSO4 The ppt. is insoluble

Sulfite; SO32 White BaSO3The ppt. dissolvesto give SO2(g) an acidic gas .

Carbonate;CO32 White BaCO3 The ppt. dissolves with effervescence& a colourless solution BaCl2(aq)

Aluminiumpowder

AmmoniaNH3gas

NO3

Damp red litmus

paper turns blue

heat heat

NH4+

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Halide ions

Chloride

Cl-

Add HNO3/AgNO3(aq)

OR

Giveswhite ppt.(AgCl) with Ag+(aq) whichis soluble in dilute & Conc. NH3

Ag

+

(aq) + Cl

(aq)

AgCl(s)

Add HNO3 / Pb(NO3)2(aq) Pb2+(aq) + 2Cl(aq) PbCl2 (s)

white ppt

Bromide

Br -

Add HNO3/AgNO3(aq)

OR

Add HNO3 / Pb(NO3)2(aq)

Givespale cream ppt.with Ag+(aq) which is :Ag

+(aq) + Br

(aq) AgBr(aq)

o partially soluble inNH3(aq)o completely soluble in conc.NH3

Pb2+

(aq) + 2Br(aq) PbBr2(aq)off-white ppt

Iodide

I -

Add HNO3/AgNO3(aq)

OR

Add HNO3 / Pb(NO3)2(aq)

GivesPale yellow ppt.with Ag+(aq)Which isinsoluble in dilute orconc.NH3(aq)

Ag+(aq) + I

(aq) AgI(s)AgI isinsoluble in both concentrated and diluteammonia NH3

Pb2+ (aq) + 2 I(aq) PbI2 (s)bright yellow ppt.

Effect of aq.

AgNO3 Effect of aq. (dilute)NH3 Effect ofConc. ammonia

Cl(aq)

chloride

Whi te ppt .

AgCl

The ppt. dissolves forming acolourless solution

AgCl + 2NH3(aq)

[Ag(NH3)2]+(aq) + Cl

(aq)

The ppt . dissolves forminga colourless solution

AgCl+ 2NH3(conc.)

[Ag(NH3)2]+(aq) + Cl

(aq)

Br(aq)

Bromide

Cream pp t.AgBr

remains insolubleThe ppt. is Soluble & dissolves

forming a colourless solution

AgBr + 2NH3(conc)

[Ag(NH3)2]+

(aq) + Br

(aq)

I(aq)

Iodide

Pale yel lowppt.AgI

remains insoluble(No further change to the pale

yellow ppt.)

remains insoluble

(No further change to the paleyellow ppt.)

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Silver nitrate solution

AgNO3(aq) is used to test for the presence ofhalide ions in solution.

Anion ppt. Addition of Ammonia NH3

Colour formula dilute concentrated

Chloride ; Cl

White AgCl dissolves to givecolourless solution

dissolves to givecolourless solution

Bromide ; Br Cream AgBr Slightly soluble

dissolves to give

colourless solution

Iodide ; I Yellow AgI insoluble Insoluble

AgCl ppt. dissolves in bothdilute and conc. ammonia forming a colourless solution of

diammine silver(I)ion complex.

AgCl + 2NH3(aq) Ag(NH3)2+(aq) + Cl(aq)

White ppt. colourless solution

Why the solution of the halide sample is kept acidicwith nitric acid HNO3 during

the precipitation?

The nitric acid reacts with, and removes, other ions that might also give a white

precipitate with silver nitrate e.g Ag2CO3.

Ag2CO3(s) + 2HNO3(aq) 2AgNO3(aq) + H2O(liq) + CO2(g)

AgX with sunlight Photodecomposition

F Cl Br I

Silver halide AgF AgCl AgBr AgI

Effect ofsunlight onsilver halide

No effect whitegreythe ppt. darkens

creamyellow/greenthe ppt. darkens

remains yellow

To eliminate possible interference from anions (e.g CO3

) that can also

form insoluble silver salts.

Ag(aq) + X

(aq) AgX(s)

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Act ion of co ncentrated s ul fur ic ac idon hal ide salts :

Halide salts react with conc. H2SO4 to give steamy fumes hydrogen halide HX(g) in

moist air & hydrogen sulfate (or sulfate).

The reaction is hazardous & must carried on small scale and in a fume cupboard.

Steamy white fumes

Conc. H2SO4 displaces hydrogen chloride from sodium chloride:

NaCl(s) + H2SO4(liq) NaHSO4(s) + HCl(g)Steamy white fumes

HBr can be displaced from KBr :KBr(s) + H2SO4(liq) KHSO4(s) + HBr(g)

Steamy white fumesbut some of the HBr is oxidised by conc. H2SO4

2HBr(g) + H2SO4(l) Br2(g) + 2H2O + SO2(g) oxidation of HBr

-1 +6 0 +4Brown fumes

SO2(g) is a colouless gas it cant be seen!SO2(g) turns a filterpaper soaked with acidified K2Cr2O7from orangeto green.

HI can be displaced from KI :KI(s) + H2SO4(liq) KHSO4(s) + HI(g)

Steamy white fumesConc. sulfuric acid also oxidises HI but the reaction goes further as HI is a better reducing agent.

Hydrogen sulfide has a rotten egg smell.

8HI(g) + H2SO4(l) 4I2(s/g) + H2S(g) + 4H2O(l) oxidation of HI

-1 +6 0 2

NaX(s) + H2SO4(liq) NaHSO4(s) + HX(g)

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Conc.

H2SO4

Halide Observation on Adding Conc. H2SO4 reaction products

Chloride ; Cl white steamy fumes in cold HCl(g)Blue damp litmus turns red

Bromide ; Br white steamy fumes in cold Brown ororange fumes

HBr(g)Br2(g)

Iodide ; I

white steamy fumes in cold purple fumes black solid (on test tube walls) yellow solid Bad egg smell

HI(g)I2(g)I2(s)S8(s) or S(s)H2S(g)

Simple chemical tests for the Halogens X2

Element Colourin waterColour in hydrocarbon

solvent(e.g hexane) orVolasil

chlorine Paleyellow pale yellowishgreen

Bromine Yellow (brown) RedOrange

Iodine brown purple

Chlorine Cl2turns blue litmusred then bleaches it. Cl2 displaces bromine and iodine from bromide or iodide solutions.

Cl2(aq) + 2NaBr(aq) 2NaCl(aq) + Br2(aq)

Cl2(aq) + 2KI(aq) 2KCl(aq) + I2(aq)

Bromine displaces iodine from an iodide solution.

Br2(aq) + 2KI(aq) 2KBr(aq) + I2(aq)

Iodine turns starch blue black.

HCl(g) white fumes

HBr(g) white fumes ; SO2(g) ; Br2 (g) orange fumes ;

HI(g) white fumes ; H2S(g) smell ofbad eggs ;

I2 (g/s) purple fumes & grey solid ; S8 yellow solid

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Flame colou rs

Metal

ion

Lithium

Li+

Sodium

Na+

Potassium

K+

Magnesium

Mg2+

Calcium

Ca2+

Strontium

Sr2+

Barium

Ba2+

Flame

colourRed Yellow

persistent

Lilac Colourless

No colour (Brick)Red CrimsonRed

green

How you can carry out a flame test?

1. Take 45 drops ofconc. HClon a watch glass.[chlorides salts are very volatile than others].

2. Make the Nichrome wire red hot and dip it into the acid and then heat

again until there is no colour is seen when the wire is in the flame.[

3. Moisten the head of the Nichrome wire with the conc. HClacid

4. Dip in the sample and then place it in the hottest roaring part of the flame.

5. Observe the flame. Repeat the steps if necessary.

Reasons for us ing Nichrom e wire:

chemically Unreactive

stableathigh temperaturesin air and with HCl acid

does not colour the flame.

1. Calcium compounds produce yellow red (brick-red) flame butmagnes iumcompounds do no t. Explain the difference.

2. A flame test formore than ONE cation is not reliable or possible ( e.g Na+ and Ba2+).Explain why.

The difference in energyE = h c/ between the exited energy level and theground state is NOT within the visible spectrum for Mg2+ ions.

since ONE flame hidesor obscures the other flame (e.gyellow is longerlasting

than the apple green colour.

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Thermal decoposi t ion

Thermal Stability of Group I & II Nitrates NO3&Carbonates( CO32

) :

Group II nitrates M(NO3)2 decompose on heating to produce a metal oxide

(MO), a brown nitrogen dioxide NO2 gas and

oxygen gas.

Ba(NO3)2 >> Sr(NO3)2 > Ca(NO3)2 > Mg(NO3)2 >>Be(NO3)2

2 Mg(NO3)2(s) 2MgO(s) + 4 NO2(g) + O2(g)Magnesium nitrate magnesium oxide brown gas

Group I nitrates MNO3 [ other than Li]:All decompose on heating, except LiNO3 ,to produce a metal

nitrite MNO2, and oxygen gas.

KNO3(s) heat KNO2(s) + O2(g)potassium nitrate potassium nitrte

Exception ( with lithium nitrate)

4 LiNO3(s) heat 2Li2O(s) + 4 NO2(g) + O2(g)lithium nitrate lithium oxide nitrogen dioxide

(acidicbrown gas)

Above 70 C, sodium bicarbonate decomposes into sodium carbonate,

waterand carbon dioxide.

2 NaHCO3 heat Na2CO3 + H2O + CO2

M(NO3)2(s) MO(s) + 2NO2(g) + O2(g)

MNO3(s) heat MNO2 + O2(g)

ExceptLiNO3
http://en.wikipedia.org/wiki/Sodium_carbonatehttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Sodium_carbonate

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Group II carbonates ( MCO3 ) They decompose on heating to produce a metaloxide (MO and CO2)

at room temperature BeCO3(s) BeO(s) + CO2(g)

at 540oC MgCO3(s) MgO(s) + CO2(g)

at 1360oC BaCO3(s) BaO(s) + CO2(g)

BaCO3 SrCO3 CaCO3 MgCO3 BeCO3

Note: Both nitrates M(NO3)2(s) and carbonates MCO3(s) become more

thermally stable down the Group

Carbonates of Group 1; M2CO3

Group I carbonates M2CO3 do not decompose at normal Bunsen

burner temperature except Li2CO3

Li2CO3(s) heat Li2O(s) + CO2(g)

Na2CO3 does not decompose at all but it melts at 850oC.

MCO3 s MO s + CO2

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Investigating the trend (ease) in the thermal stability of thecarbonate MCO3 of the elements of group 2

The rate of CO2(g) gas production is slower down the group soThe carbonates become more thermally stable down a group.

Amount of metal

carbonate MCO3used / moles

Mass of metal carbonate

MCO3 used / g

m = n Mr

Volume ofCO2

gas produced after

2 minutes / cm3

MgCO3 2.5103

2.5103

84 = 0.21g

CaCO3 2.5103 2.5103 100 = 0.25g

SrCO3 2.5103

2.5103

147.6 = 0.37g

BaCO3 2.5103

2.5103

197 = 0.50g

Heat

D

ecreasing

volume

100 cm graduatedsyringe

Use the same number ofmoles ofmetal carbonate MCO3

Heat each carbonate separatelyin a test tube in an identical manner.

Keep the test tube at the same height (or same position)

Keep Bunsen in the same position,

Use the same flame strength i.e always use roaring flame.

Measure & record the volume of CO2(g) collected in the gas syringeafter2 minutes(same time).

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QuestionA student investigated the ease with which Group 2 metal carbonates thermally

decompose when heated with a Bunsen burner.

XCO3(s) XO(s) + CO2(g)

(a) Each test tube must be heated directly by a Bunsen flame in an identical manner.

Suggest how this can best be achieved.

(b) In each experiment, the student used the same number of moles of metal

carbonate.

The mass of magnesium carbonate, MgCO3, heated was 0.21 g.

Calculate the mass of barium carbonate, BaCO3, that should be used for a valid

comparison.

(c) The following results were obtained after heating each sample for two minutes.

Metal carbonate in

the test tube

Volume of gas

produced/ cm3

None 9

MgCO3 20

CaCO3 13

SrCO3 11

BaCO3 9

(i) Why was a test tube containing no metal carbonate heated? (1)

(ii) Use the results in the table to describe the trend in thermal stability of the Group 2metal carbonates. (2)

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Reactions of acids

1. acids with metal carbonates

CaCO3(s) + 2HCl(aq) CaCl2 + H2O + CO2(g)

CaCO3(s) + 2CH3COOH(aq) Ca(CH3COO)2 + H2O + CO2(g)

Na2CO3 + 2HCO2H(aq) 2NaHCOO

+ H2O + CO2(g)

Ionic Equation

2. acids with metal hydrogencarbonates

KHCO3(s) + HCl(aq) KCl + H2O + CO2(g)

Ionic Equation

3. acids with metal oxides

CaO(s) + 2HCl(aq) CaCl2 + H2O

White solid colourless solution

CuO(s) + 2HNO3(aq) Cu(NO3)2 + H2OBlack solid blue solution

Metal carbonate + acid salt + water+ carbon dioxide

CO32(aq) + 2H

+(aq) H2O + CO2(g)

Metal oxide + acid salt + water

Metal hydrogencarbonate + acid salt + water + carbon dioxide

HCO3(aq) + H+(aq) H2O + CO2(g)

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4. acids with metals (above H)

[ Mg ; Zn . . . etc.]

Mg(s) + 2HCl(aq) MgCl2 + H2(g)

Zn(s) + H2SO4(aq) ZnSO4 + H2(g)

Ionic Equation

5. acids with sulfite salts

Ionic Equation

BaSO3(s) + 2HCl(aq) BaCl2(aq) + H2O + SO2(g)

Summary of Act ion of di lute acids

Action ofacid LIKELY CAUSE

Inference

CO2 gas evolved Carbonates orhydrogencarbonates of metalsother than Group 1*

CaCO3 heat CaO + CO2(g)

NH3 Ammonium salts

Sulfur dioxide SO2 evolved on warming Sulfite

SO32(aq) + 2H (aq) heat H2O + SO2

Sulfur dioxide SO2

and pale yellow ppt.

formed thiosulphate

Hydrogen A metal ( above Hydrogen) e.g Zn, Mg, Fe..

Nitrogen dioxide NO2 evolved2NO2

+ 2H

+ H2O + NO(g) + NO2(g)

nitrite

M(s) + 2H+(aq) M2+ (aq) + H2 (g)

SO32

+

2H

+

(aq)heat

H2O + SO2(g)

Metal + acid salt + hydrogen

Sulfite salt + acid salt + water + sulfur dioxide

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* To distinguish between carbonate & hydrogencarbonate HCO3

TEST OBSERVATIONS

Carbonate Hydrogencarbonate

on aqueous solution CO3

HCO3

pH 12 14 8 9

boil No changeCO2 evolved &

pH increases to 1214

Add aqueous solution of

MgSO4 or Ca2+

(aq)

Immediate ppt. at room

temp.

No ppt. at room temp.

A white ppt. only forms on

boiling.

Sodium hydroxide solution

Observation on adding

NaOH(aq)

Observation on adding

EXCESS NaOH(aq) Likely ions

White ppt.

ppt. dissolves to give a

colouless solution

Pb2+ ; Zn2+ ; Al3+

Whiteppt. ppt. is insoluble Mg2+ ; Ca2+ ; Sr2+

No ppt. Na+

; K+

;

No ppt. but NH3evolved

NH4+

NH4+

(aq) + OH

(aq) NH3(g) + H2O(l)

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Q u e s t i o n s

1. Complete the table below.

Observation expected for a

positive resultReagents or testGas

Glowing splintOxygen

Carbon dioxide

Solution turns from

. . . . . . . . . . .to . . . . . . . . . . . . .

Potassium dichromate(VI)

solution acidified withdilute sulfuric acid

Sulfur dioxide

Turns red and is thenbleached white

Moist blue litmus paper

2. Salt D contains one cation and one anion.

Complete the table, giving tests and observations to show that ammonium ions,NH4+, is

present in D.

Test Observation Inference

NH4+, ions

(ii) Complete the inference statements in the table below.


Aqueous barium chloride isadded to a solution ofD.

Dilute hydrochloric acid isthen added.

White precipitate isformed which does

not dissolve in dilutehydrochloric acid.

The precipitate is

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

Therefore the anion in D is

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

(2)

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3. A series of tests was carried out on a white solid X.

In the tables below complete the inferences.

(a) A flame test was carried out on X.

InferenceObservation

The metal ion is.........................................The colour of the flame was green

(b) Dilute sulfuric acid was added to an aqueous solution ofX.


The precipitate is ....................................................White precipitate

(c) X was heated, very strongly.


The gas is ................................................................A brown gas was evolved.

(d) A sample ofX was warmed with aqueous sodium hydroxide and aluminium powder.


The gas is ...............................................................

The anion in X is ....................................................

A gas was evolved which turned

red litmus blue.

(e) The formula ofX is ...........................................................................

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4. A student was given three aqueous solutions P, Q, and R. Complete the

test and observations which lead to the conclusions.

test Observation conclusion

(a) To a few cm3 ofP, dilutenitric acid and aqueousbarium nitrate were added.

P contains SO42

(b) To a few cm3 ofQ dilute

hydrochloric acid wasadded.

The gas given off wastested.

Q contains CO32

ions

(c) yellow precipitate R containsI

Iodide ions.

5. Describe tests you would use to distinguish between the following pairs ofcompounds.Include the results you would expect foreach compound.

(a) Sodium nitrate, NaNO3, and ammonium nitrate, NH4NO3.

(b) Sodium carbonate, Na2CO3, and sodium hydrogencarbonate, NaHCO3.

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6. For each compound in the pair, describe the observations you would expect to makewhen the test is carried out. If a gas is evolved, include the name of the gas.

(a) Solid sodium chloride and solid potassium chloride.

Test: Flame test.

Observation with sodium chloride: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Observation with potassium chloride: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Aqueous potassium sulfate and aqueous potassium sulfite.

Test: Addition of dilute hydrochloric acid followed by aqueous

barium chloride.

Observation with potassium sulfate: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Observation with potassium sulfite: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

(c) Solid ammonium sulfate and solid potassium sulfate.

Test: Warm with aqueous sodium hydroxide, testing any gas

with damp red litmus paper.

Observation with ammonium sulfate : . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Observation with potassium sulfate: : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

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(d) Solid sodium chloride and solid sodium bromide.

Test: Add concentrated sulfuric acid, testing any gas evolved

with damp blue litmus paper.

Observation with sodium chloride: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Observation with sodium bromide: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

7. The tables below show a series of simple tests on different compounds. Fill in the spaces

in the tables.


The flame test was carried

out on solid A.Potassium ions present in A.


To an aqueous solution of

B,add . . . . . . . . . . . . . . . .

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

followed by. . . . . . . . . . . .

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

A yellow precipitate was

produced that wasinsoluble in concentrated

ammoniasolution.

Iodide ions present in B.


Add dilute hydrochloricacid to solid C. Heat the

mixture and pass the gas

through acidified potassium

dichromate(VI) solution.

Orange solution goes

green.

Gas evolved . . . . . . . . . . . . .

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

Anion in C . . . . . . . . . . . . .

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

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3B _ 6B -Test for ions 2013