Unit Questions

1.

(a) Fe Fe2+

(i)

Give the electron configuration of:

[Ar] ......................................................................................................... [Ar] .........................................................................................................(1)

(ii)

Draw the structure of the hexaaquairon(II) ion, [Fe(H2O)6] , clearly showing its shape.

2+

(1)

(iii)

Give the equation for the complete reaction of hydroxide ions with a solution of hexaaquairon(II) ions.

(1)

(iv)

State what you would see if the product mixture in (iii) is left to stand in air. ........................................................................................................................... ...........................................................................................................................(1)

The Crossley Heath School

1

(b)

Consider the equation for the half reaction Fe (i)2+

+ 2e

Fe

E = 0.44 V

Define the term standard electrode potential with reference to this electrode. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(ii)

Explain why the value of E suggests that the iron will react with an aqueous 2+ solution of an acid to give Fe ions and hydrogen gas. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

State why E values cannot predict that a reaction will occur, only that it is possible. ........................................................................................................................... ...........................................................................................................................(1) (Total 10 marks)


2

2.

Read the passage below carefully and answer the questions which follow. Stained glass and gemstones Many medieval churches contain some very fine examples of stained glass coloured with transition metal compounds. Blue and green colours result from adding cobalt or copper oxides to molten glass. Copper oxide is added to colour the glass red, but it must be mixed with a strong reducing agent to give this colour. The red colour is so strong that it can appear black, and may need to be coated as a thin layer on top of colourless glass. Like glass, many gemstones are based on silica and some on alumina. They are also coloured by transition metal compounds. A solid matrix of either silica, SiO2, or alumina, Al2O3, has some of the silicon or aluminium replaced by a small quantity of a transition metal. Replacing about 5% of the aluminium ions in alumina with chromium(III) gives ruby, important in laser production. Replacement of aluminium ions by a mixture of iron(III) and titanium(III) gives sapphire. The metal coming in must have the same charge and about the same radius as the aluminium.Based on Colour, A Chemical Overview Chemistry Review volume 5, number 5, May 1996 written by Ken Kite

(a)

The metals imparting colour to glass and gemstones mentioned in the passage are all transition elements. (i) Define what is meant by a transition element. ........................................................................................................................... ...........................................................................................................................(1)

(ii)

Explain the processes which lead to hydrated transition metal ions being coloured. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)


3

(b)

(i) glass.

Give the formulae of the copper oxide which causes the red colour in

...........................................................................................................................(1)

(ii)

The production of red copper oxide is involved in a test for a functional group in organic chemistry. Name the reagent used in this test and the functional group it detects. Reagent ............................................................................................................. Functional group ...............................................................................................(2)

(c)

Why would the addition of iron(II) oxide, FeO, or osmium(III) oxide, Os2O3, not replace aluminium ions in alumina? ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(d)

(i) Starting with a chromium(III) compound, state how it could be converted into a chromium(VI) compound, a chromium(II) compound and a complex ion. You should include equations and colour changes in your answer. (Allow one and a half lined pages)(7)


4

(ii)

Discuss the chemistry of the use of chromium salts in breathalysers. Explain why they are no longer used and describe the chemistry of one modern type of breathalyser. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(4) (Total 20 marks)

3.

Many modern day fabric softeners are manufactured with the liquid enclosed in a water soluble capsule. The capsule is based on a polymer of ethenol. (a) Explain why poly(ethenol) is soluble in water. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)


5

(b)

Poly(ethenol) is made by hydrolysing poly(vinyl acetate), PVA, [C4H6O2]n. (i) Draw the repeat unit of poly(ethenol) ....................................................................................(1)

(ii)

Write the formula of the monomer which polymerises to form poly(vinyl acetate), PVA (poly(ethenylethanoate)). ....................................................................................(1)

(c)

(i) 1,2-dibromocyclohexane reacts with ammonia to produce compound A, C6H14N2. Give the structural formula of A.

(1)

(ii)

Compound A reacts with hexanedioyl dichloride to produce a polymer. Draw the structure of the repeating unit of this polymer.(2)


6

(iii)

Suggest why this polymer cannot be made into strong fibres. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(d)

Classify the two polymerisation reactions. Poly(ethene) ................................................................................................................ Fibre ............................................................................................................................(1) (Total 10 marks)

4.

(a) (i) Write the equation for the reaction between cyclohexene, and bromine.

,

(1)


7

(ii)

Draw out the mechanism for this reaction.

(3)

(b)

(i) Write the equation for the reaction between benzene, , and bromine in the presence of a catalyst of anhydrous iron(III) bromide, FeBr3. ...........................................................................................................................(1)


8

(ii)

Draw out the mechanism for this reaction. Include an equation for the formation of the species that attacks the benzene ring.

(4)

(iii)

Write an equation to show how the catalyst is regenerated. ...........................................................................................................................(1)

(c)

Comment critically on: (i) the differences and similarities of the first steps involving the organic compounds in both reactions. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)


9

(ii)

why the two intermediates formed in these first steps then react differently? ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(d)

State the number of peaks in the proton nmr spectrum of the product of the reaction between cyclohexene and bromine. .....................................................................................................................................(1) (Total 17 marks)

5.

A firm claims that their iron tablets contain 10 mg of Fe per tablet. A chemist wishes to check this by titration using potassium manganate(VII) and dilute sulfuric acid. Fe (aq) 2+

2+

Fe (aq) + e+

3+

2+

MnO4 (aq) + 8H (aq) + 5e

Mn (aq) + 4H2O(l)

(a)

Why is the acid necessary? ..................................................................................................................................... .....................................................................................................................................(1)

(b)

How many moles of Fe

2+

react with one mole of MnO4 ?(1)

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


10

(c)

Each tablet contains 10 mg of Fe . (i) How many moles of Fe2+

2+

are in one tablet?

(1)

(ii)

Use your answer to (i) to calculate the volume of 0.010 mol dm potassium manganate(VII) solution that would be needed to react with one tablet.

3

(2)

(iii)

Is this a suitable volume to verify the integrity of the firms claim? How would you alter the experiment to obtain a more suitable volume? ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


11

(d)

The recommended consumption of Fe per day is 14 mg. The tolerable upper level of 2+ consumption of Fe per day is 45 mg. The 10 mg iron tablets produced by a pharmaceutical company contain between 9 and 2+ 11 mg of Fe . Discuss whether or not this range of iron content is acceptable. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 8 marks)

2+

6.

Select, from AD, the type of interaction which best describes the bonding between (a) adjacent polymer chains in [CH2CH2]n A B C D dative covalent London forces ion-dipole ionic(1)


12

(b)

copper ions and ammonia in Cu(NH3)4 A B C D dative covalent London forces ion-dipole ionic

2+

(1) (Total 2 marks)

7.

Two compounds may be similar in that they both have A B C D dative covalent bonds in their molecules at least one bond angle of 120 in each molecule non-polar molecules linear molecules

Select from AD, the similarity between each of the compounds below. (a) Benzene, C6H6 and cyclohexane, C6H12 A B C D(1)


13

(b)

Hydrogen cyanide, HCN, and carbon dioxide, CO2 A B C D(1) (Total 2 marks)

8.

This question is about the following organic compounds: A B C D Benzene, C6H6 Glycine, NH2CH2COOH Propene, CH3CHCH2 Propanone, CH3COCH3

Select, from AD, the compound which would (a) be a solid at room temperature A B C D(1)

(b)

give a salt by reaction with sodium hydroxide A B C D(1)


14

(c)

give a sulfonic acid by reaction with fuming sulfuric acid A B C D(1)

(d)

form a precipitate when reacted with 2,4-dinitrophenylhydrazine A B C D(1) (Total 4 marks)

9.

When the colourless liquid chlorobenzene is shaken with bromine water, the chlorobenzene becomes a yellow orange colour. What is the interpretation of this? A B C D an addition compound of chlorobenzene and bromine has formed. the chlorine atom has been replaced by a bromine atom. a hydrogen atom has been replaced by a bromine atom. the bromine is more soluble in chlorobenzene than in water.(Total 1 mark)


15

10.

When hydrogen cyanide, HCN, is added to ethanal, CH3CHO, the resulting solution has no effect on the plane of polarisation of plane polarised light. This is because A B C D ethanal is not chiral the product is not chiral the intermediate is planar the product is a racemic mixture(Total 1 mark)

11.

The rate equation for the reaction between aqueous sodium hydroxide and 2-chloro-2-methylpropane is Rate = k[2-chloro-2-methylpropane] The first step in the mechanism of this substitution reaction is A B C D nucleophilic attack by OH ions on the carbon atom in the CCl bond electrophilic attack by OH ions on the carbon atom in the CCl bond the breaking of the CCl bond to form a carbocation the simultaneous making of a OC bond as the CCl bond breaks(Total 1 mark)

12.

The optical isomers of alanine, CH3CH(COOH)NH2 A B C D have different melting points rotate the plane of plane polarised light in opposite directions react at different rates with ethanoyl chloride, CH3COCl both occur naturally in protein molecules(Total 1 mark)


16

13.

Which chemical term best describes what happens, when butylamine is added to a solution of a copper(II) salt? A B C D precipitation redox proton transfer complex formation(Total 1 mark)

14.

The substance of formula (OCH2CH2OOCC6H4COOCH2CH2OOCC6H4CO)n is a A B C D polyester natural oil or fat detergent protein(Total 1 mark)

15.

What class of organic compound has a characteristic smell and gives a solution in water with a pH of about 10? A B C D arene amine aldehyde carboxylic acid(Total 1 mark)


17

16.

X, Y, and Z are three different compounds from the list below. X and Y react together to form an ester. X and Z also react to give the same ester as X and Y, but less readily. Compound Y could be A B C D propanoyl chloride propanoic acid propan-1-ol propanal(Total 1 mark)

17.

Which of the following isomers of C4H10O has a chiral centre? A B C D Butan-1-ol Butan-2-ol 2-methylpropan-1-ol 2-methylpropan-2-ol(Total 1 mark)

18.

In a standard hydrogen electrode A B C D the hydrogen gas is at one atmosphere pressure a solution of 1 mol dm sulfuric acid is used a temperature of 273 K is maintained a piece of shiny platinum foil is used(Total 1 mark)3


18

19.

The standard electrode potential for the electrode system based on the equation below is +1.51 V. MnO4 (aq) + 8H (aq) + 5e +

Mn (aq) + 4H2O(l)

2+

Which of the following statements about the electrode system is correct? A B C D the electrode potential at pH 5 is +1.51 V. Mn (aq) is acting as an oxidising agent. changing the concentration of Mn (aq) would cause a change in the electrode potential. the electrode used in this half-cell is made of manganese.(Total 1 mark)2+ 2+

20.

Which of the following is always proportional to Ecell for a chemical reaction? A B C D Hr Ssystem Ssurroundings Stotal(Total 1 mark)

21.

Which of the following ground state electron configurations corresponds to an element most likely to form an oxide with catalytic properties? A B C D 1s 2s2 2 2 2 2 2 2 2 6 6 6 2 2 2 2 6 5 2

1s 2s 2p 3s

1s 2s 2p 3s 3p

1s 2s 2p 3s 3p 3d 4s

(Total 1 mark)


19

22.

Methanol can be vigorously oxidised with an acidified solution containing dichromate(VI) ions, 2 Cr2O7 , to form methanoic acid and chromic(III) ions. (a) What are the oxidation numbers of carbon in methanol and methanoic acid? MethanolMethanoic acid A B C D 1 2 +1 +2 +1 +2 1 2(1)

(b)

How many moles of methanol react with one mole of dichromate(VI) ion, Cr2O7 ? A B C D 1 1 3(1) (Total 2 marks)

2

23.

Which of the following will not act as a ligand in the formation of complexes? A B C D C6H5NH2 CH3NH2 NH4 NH3(Total 1 mark)+


20

24.

(a) The conversion of butan-2-ol to 2-bromobutane can be performed as outlined below: Butan-2-ol is heated with a mixture of 50 % aqueous sulphuric acid and sodium bromide for 45 minutes. The crude 2-bromobutane is distilled off. The crude 2-bromobutane is shaken with pure water, which removes the sulphuric acid and some of the butan-2-ol that contaminates the product. The organic layer is separated and then shaken with concentrated hydrochloric acid to remove residual butan-2-ol. The organic layer is then shaken with dilute sodium carbonate solution. Anhydrous calcium chloride is added to the organic layer and allowed to stand for some hours. The organic layer is then redistilled in a dry apparatus.

(i)

Explain, in terms of kinetic factors, why the mixture is heated for a significant amount of time. ........................................................................................................................... ...........................................................................................................................(1)

(ii)

Why is sulphuric acid necessary in the reaction mixture? ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

Suggest why butan-2-ol, which is only partially miscible with water, is much more soluble in concentrated hydrochloric acid. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


21

(iv)

Why is the organic layer shaken with dilute sodium carbonate solution? ........................................................................................................................... ...........................................................................................................................(1)

(v)

What is the purpose of the anhydrous calcium chloride? ...........................................................................................................................(1)

(vi)

How would you heat the mixture safely? Explain your choice of method. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


22

(b)

Both 2-bromobutane and butan-2-ol are chiral molecules. If one optical isomer of 2-bromobutane is used to make butan-2-ol by reaction with aqueous hydroxide ions, the product mixture is not optically active. The mechanism for the reaction is either SN1 or SN2; these are given below

S

N

1 H C

C3

2H

C B r

3H

C H3

2H

C +

3H

C H C2H

C

+

C H

: B

r

C +

3H

C

2H

C O H

3H

H

3

C

+

C H

: O

H

H

3

C

C H

S

N

2

H

O H

: C

C3

2H

C B r

3H

C H H O3

2H

C B r

3H

C H

C C H

C H O C C

2H

C H

3H

+

: B

r

3H


23

Explain which one of these mechanisms is consistent with the lack of optical activity in the product mixture. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)

(c)

The oxidation of butan-2-ol with hot potassium dichromate(VI) in acidic solution produces butanone, CH3COCH2CH3. (i) What would you see as the reaction proceeds? ...........................................................................................................................(1)

(ii)

The dichromate(VI) ion is reduced under these conditions to chromium(III) ions. The half-equation for the oxidation of butan-2-ol to butanone is CH3CH(OH)CH2CH3 CH3COCH2CH3 + 2H + 2e+

Write the ionic half-equation for the reduction of dichromate(VI) ions, and hence derive the overall equation for the oxidation of butan-2-ol. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


24

(iii) S 1

The IR spectra of butan-2-ol and of the organic product from its oxidation with dichromate(VI) ions are given below. p 0 e c t r u 0 m o f b u t a n - 2 - o l

T ra n s m itta n c e /%

5

0

0 4

0

0

0

3

0

0

0 1

2

0

0

0

1

W a v e n u m b e r/c m

S 1

p 0

e c t r u 0

m

o

f

t h

e

o

r g

a n

i c

p

r o

d

u

c t

f r o

m

t h

e

o

T ra n s m itta n c e /%

5

0

0 4

0

0

0

3

0

0

0 1

2

0

0

0

1

W a v e n u m b e r/c m Bond CH (alkanes) CH (alkenes) C=O (aldehydes, ketones, carboxylic acids) Wavenumber/cm 28503000 30003100 168017501

Bond CO (alcohols, esters) OH (hydrogenbonded alcohols) OH (hydrogenbonded carboxylic acids)

Wavenumber/cm 10001300 32303550 25003300

1


25

What evidence is there from the spectra that the reaction in part (ii) has occurred? ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(d)

When potassium dichromate(VI) is dissolved in water, the following equilibrium is set up Cr2O7 (aq) + H2O(l) (i)2

2CrO4 (aq) + 2H (aq)

2

+

If a solution of barium ions is then added to this solution, solid barium chromate, BaCrO4, is precipitated; it is sparingly soluble in water, so the equilibrium given below also exists in the solution Ba (aq) + CrO4 (aq)2+ 2

BaCrO4(s)

Explain what happens to the pH when the barium ions are added. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


26

(ii)

If a solution of lead(II) ions is added instead of barium ions, solid PbCrO4 is precipitated. This is almost completely insoluble in water so all chromate(VI) ions are removed from solution Pb (aq) + CrO4 (aq) PbCrO4(s) State how the pH of this solution differs from your answer in part (i). ........................................................................................................................... ...........................................................................................................................(1) (Total 20 marks)2+ 2

25.

For a redox reaction to be thermodynamically feasible, Ecell must be A B C D positive negative greater than +0.3 V more negative than 0.3 V(Total 1 mark)

26.

The drug ibuprofen can be synthesised from benzene by the route shown below.

C H CS t A p e

3H

C C3 H C H CS t B p e

3H

C C3 H C H CS t C p e

3H

C C3 H C H CC O / P d c a t a l y s t

3H

C32H

C

H

2H

2H

2H

C C3H

O

H

C3H

C

H O H C I b u3H

C2

C

O

H

p

r o f e n


27

(a)

Name the type and mechanism of the reaction in Step A, and suggest a suitable reagent and catalyst. Type and mechanism .................................................................................................. Name of the reagent for Step A .................................................................................. Catalyst .......................................................................................................................(3)

(b)

Step C is a reduction. Give ONE reason why lithium tetrahydridoaluminate, LiAlH4, is preferred to hydrogen as a reducing agent in this reaction. ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)


28

(c)

A sample of the final product was analysed by combustion. 1.00 g was burnt in oxygen. It produced 2.78 g carbon dioxide and 0.786 g water. State the molecular formula of ibuprofen and show that these results are consistent with it.

(4)


29

(d)

Ibuprofen can be analysed by instrumental methods. The infrared spectra of ibuprofen and two other drugs, aspirin and paracetamol, not necessarily in that order, are shown opposite.C H C I b u p r o f e n h2H 3H

C3

C

H

a s

t h

e

f o

r m

u

l a

H

C C3H

C2

C

O

H

2O

H t h O e

O C fCo H m r 3 u l a

A

s p

i r i n

h

a s

O

H

P

a r a c e t a m H

o

l N

h C O

a s3H

t h C

e

f o

r m

u

l a

(i)

Explain, referring to the structure of each molecule, why infrared spectroscopy is not a good technique to distinguish aspirin from ibuprofen. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


30

(ii)S p

Deduce which of X, Y or Z is the infrared spectrum of paracetamol, giving a piece of evidence from the spectrum you select.m 1 0 X 0

e c t r u

T ra n s m itta n c e (% )

5

0

0 4 0 S p e c t r u m 1 0 Y 0

0

0 W

2 a v

0

0 30 0 0 0 e n u 1 m b e r / c m


5

0

0 4 0 S p e c t r u m 1 0 Z 0

0

0 W

2 a v

0

0 30 0 0 0 e n u 1 m b e r / c m


5

0

0 4 0

0

0 W

2 a v

0

0 30 0 0 0 1 1 e n u m b e r / c m

0

0

0


31

........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)

(iii)

Ibuprofen and aspirin can be distinguished using their mass spectra. A line at mass/charge ratio 57 occurs only in the mass spectrum of ibuprofen. Give the formula of the ion which produces this line. ........................................................................................................................... Suggest the mass/charge ratio of one line which occurs in the mass spectrum of aspirin but not ibuprofen, and the formula of the species which produces it. ........................................................................................................................... ...........................................................................................................................(3) (Total 14 marks)

27.

An important industrial compound, S, has the formula C12 H S

25

3

ON a +

(a)

(i) Name the reagents and give the conditions where necessary for the two steps needed to make

S

3

ON a +

f r o

m

b

e n

z e n

e .

Step 1 Reagent .................................................................................................. Conditions ................................................................................................. Step 2 Reagent ..................................................................................................(3)

(ii)

Name the type of reaction in each step. Step 1 ................................................................................................................


32

Step 2 ................................................................................................................(2)

(b)

(i) What is the specific name given to the reaction when an alkyl group is introduced into the benzene ring by electrophilic substitution? ...........................................................................................................................(1)

(ii)

Give the molecular formula of the reagent and of the catalyst needed to make12

H

25

C

f r o

m

b

e n

z e n

e .

Reagent ............................................................................................................. Catalyst .............................................................................................................(2) (Total 8 marks)

28.

Phenylethanoic acid occurs naturally in honey as its ethyl ester: it is the main cause of the honeys smell.C2H

C

O

O

H

The acid has the structure Phenylethanoic acid can be synthesised from benzene as follows:C H3

C H 2C l

s t e p

1

s t e p

2

C l2 ,

u

vs t e p 3 K C N

C

2H

C

O

s t e p 4 O HC o

m

A o p

u

n

d


33

(a)

State the reagent and catalyst needed for step 1. ..................................................................................................................................... .....................................................................................................................................(2)

(b)

(i)

What type of reaction is step 2?(1)

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

(ii)

Suggest a mechanism for step 2. You should include the initiation step, the two propagation steps and a termination step. You may use Ph to represent the phenyl group, C6H5.

(4)


34

(iii)

Draw an apparatus which would enable you to carry out step 2, in which chlorine is bubbled through boiling methylbenzene, safely. Do not show the uv light source.

(3) (Total 10 marks)

29.

(a) Benzene reacts with 2-bromopropane in a Friedel-Crafts reaction to give 2-phenylpropane, C6H5CH(CH3)2, usually known as cumene. C C + C 3C HH B3 r C H c u m e n H C3H 3H

+

H

B

r

e

Cumene is used to manufacture phenol and propanone.

(i)

Identify a suitable catalyst for the reaction between benzene and 2-bromopropane. ...........................................................................................................................(1)


35

(ii)

Give the mechanism for the reaction, including the formation of the electrophile.

(4)

(b)

If benzene and 1-bromopropane, CH3CH2CH2Br, are reacted under similar conditions to those in part (a), the product is still cumene although 1-phenylpropane C6H5CH2CH2CH3 might have been the expected product. C C + C 3C HH2 3H 3H

H

C

H

2

B

r c u m

C

+

H

B

r

e n

e


36

(i)

Draw the structure of the carbocation which would initially be formed.

(1)

(ii)

Suggest, in terms of relative stabilities of carbocations, what happens to the carbocation in (i) which results in cumene as the product of the reaction rather than 1-phenylpropane. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(c)

Phenol reacts with the benzenediazonium cation, C6H5N2 , in alkaline conditions to give an azo dye. (i) State the reagents needed to convert phenylamine into a solution containing + C6H5N2 ions. ...........................................................................................................................(2)

+

(ii)

Explain why the temperature of the reaction in (c)(i) needs to be kept between 0 C and 10 C. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


37

(iii)

Give the structural formula of the product from the reaction between benzenediazonium chloride and phenol.

(2)

(d)

(i) How would you show that propanone is a carbonyl compound and is a ketone, not an aldehyde? ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(ii)

A characteristic reaction of the carbonyl group, C O, is nucleophilic addition. The C C double bond reacts by electrophilic addition. Suggest the reason for the difference. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


38

(iii)

Give the mechanism for the nucleophilic addition reaction between propanone and hydrogen cyanide in the presence of a catalyst of cyanide ions, CN .


30.

(a) Cr: Cu:

(i)

Complete the electronic configurations of:

[Ar]. [Ar]..(1)


39

(ii)

The electronic configurations of chromium and of copper are not readily predictable from a consideration of the elements on either side of them in the first transition series in the Periodic Table. State how these electronic configurations differ from others in the first transition series and explain why this difference arises. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(b)

Chromium can form the ion [Cr(H2O)6] (i)

3+

in aqueous solution.

Draw the structure of this ion so as to clearly show its shape.

(1)

(ii)

How are the bonds between the water ligands and the metal ion formed? ........................................................................................................................... ...........................................................................................................................(1)


40

(iii)

Write an equation to show what happens initially when a solution containing 3+ hydroxide ions is added to a solution of [Cr(H2O)6] ions. ........................................................................................................................... ...........................................................................................................................(2)

(iv)

State what you would see as dilute sodium hydroxide is gradually added to a 3+ solution of [Cr(H2O)6] until it is in excess. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(v)

What property of chromium(III) hydroxide is shown by the reaction in part (iv)? ...........................................................................................................................(1)


41

(c)

(i) A 1.00 g sample of a metal alloy that contains chromium was 3 converted into 250 cm of an acidified solution of potassium dichromate(VI). 25.0 cm of this solution was added to an excess of potassium iodide solution. Cr2O7 + 6I + 14H 2Cr2 + 3+ 3

+ 3I2 + 7H2O3

The iodine liberated was titrated with 0.100 mol dm sodium thiosulphate solution. I2 + 2S2O3 2I + S4O6 The mean (average) titre was 37.2 cm3. Calculate the amount (moles) of iodine liberated and hence the percentage, by mass, of chromium in the alloy.2 2

(5)

(ii)

In titrations involving iodine, starch is usually added near the end-point to make the colour change clearer, although in many cases it is not really necessary. Suggest why starch is necessary in the titration in (i). ........................................................................................................................... ...........................................................................................................................(1) (Total 16 marks)


42

31.

(a) Define the term standard electrode potential, making clear the meaning of standard. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(b)

Explain why a reference electrode is needed whenever a standard electrode potential is measured. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(1)

(c)

Hydrogen peroxide decomposes in a disproportionation reaction. (i) Explain the meaning of disproportionation. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


43

(ii)

Use the following information to derive the equation for the disproportionation of hydrogen peroxide. Calculate E cell +

and explain whether the reaction is thermodynamically feasible.

O2 + 2H + 2e H2O2 + 2H + 2e+

H2O2 2H2O

E = + 0.68 V E = + 1.77 V

........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(iii)

Explain why your answer to (ii) does not necessarily show that hydrogen peroxide will disproportionate under standard conditions. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1) (Total 9 marks)


44

32.

The reaction scheme below shows a synthesis of the antiseptic, Dettol, from benzene.

B C6

e n H

z e r n e e a gW e n t6

A C6

2

m

o

l e s X o

f

r Be a g

e n

t

H

6

S

O c 3a t a l y s t Y

C 8H

10

SO

3

O B C8

H

re ag e n t Z

C C8

C

2

l

( g

)

H

1

0

S

O

3

H

1

0

O

H 3C C D l

C

3H

e t t o l

Study this reaction scheme carefully before answering any of the questions below.

(a)

(i)

Give the structural formula of A.

(1)

(ii)

Name reagent W. ...........................................................................................................................(1)

(iii)

State the type of reaction and the mechanism for the conversion of benzene into A. ...........................................................................................................................(1)


45

(iv)

Give the formula of the species which attacks benzene to form A. ...........................................................................................................................(1)

(b)

(i) Suggest the structural formula of B. You may find it helpful to study the formula for Dettol, as well as your answer to (a)(i), when answering this question.

(1)

(ii)

Give the formulae for reagent X and catalyst Y. Reagent X ........................................... Catalyst Y ...........................................(2)

(iii)

What gaseous inorganic compound will also be produced during the formation of B? ...........................................................................................................................(1)

(c)

(i)

Give the systematic name for Dettol.(1)

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


46

(ii)

Suggest why Dettol does not mix well with water. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1) (Total 10 marks)

33.

(a)

Glycine is an amino acid. C H N H2

O C

O

H H

(i)

Draw the full structural formula of the zwitterion of glycine, showing all bonds.

(1)

(ii)

Explain how the zwitterion in glycine is formed. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


47

(iii)

Use your answer to (i) to explain why glycine has a high melting temperature of 262 C. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(b)

Suggest the formula of the organic product formed when glycine reacts, under suitable conditions, with (i) hydrogen ions, H+

(1)

(ii)

hydroxide ions, OH

(1)


48

O H 3C C(iii) ethanoyl chloride,

C

l

(1)

(iv)

methanol, CH3OH

(1)

(c)

Glutamic acid is also an amino acid. The formula of glutamic acid is shown below. H H 2N C CO O H C H C H2 2

CO O H Glutamic acid exists as two optical isomers whereas glycine does not.

(i)

Why is glutamic acid chiral? ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


49

(ii)

How can the two optical isomers of glutamic acid be distinguished from each other? ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(d)

A section of the polymer nylon-6,6 is shown below O C2

O ( C 4 H ) C N

O H2

O ( 6C H ) N H C2

( 4C

H

)

C

N

H

Give the formulae of TWO monomers which could react together, under suitable conditions, to form nylon-6,6.



50

34.

Toluene is the non-systematic name of an arene widely used in industry. Its formula is C6H5CH3. Some of its reactions are summarised in the following diagram.

C

3H

BR

re B r

e a 3c tB i 2 o r n / F

3

C

3H

CR e a 2c t i o n

3H

CR M e a 4c t i o O 2n n

H

O

N

2

OR

T o l u

e ni n O4

eg R e a 5c t i o n

B

e n

z a l d

e

F u m e a 1c t i o n H 2 S

C

o m

p

o u

n

d

A C

2O

H

B

e n

z o i c

a c i d

(a)

(i)

Give the systematic name of toluene.(1)

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

(ii)

Draw a possible structural formula for compound A.

(1)


51

(b)

(i)

Name the TWO reagents needed for Reaction 2.

........................................................................................................................... ...........................................................................................................................(2)

(ii)

Give the formula of the attacking species in Reaction 2. ...........................................................................................................................(1)

(c)

(i)

Give the reaction type and mechanism in Reaction 3.

Reaction Type ........................................................................................................................... Mechanism ...........................................................................................................................(2)

(ii)

Suggest why Reactions 1, 2 and 3 all take place under milder conditions than similar reactions involving benzene. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(d)

What type of reaction does toluene undergo in Reaction 4? .....................................................................................................................................(1)


52

(e)

Name the TWO reagents needed for Reaction 5. ..................................................................................................................................... .....................................................................................................................................(2) (Total 12 marks)

35.

Vanillin, the main ingredient of vanilla essence, is one of the commonest flavouring ingredients found in foods. Synthetic vanillin, which is identical to natural vanillin, can be manufactured from methoxybenzene. One synthetic route is shown below: S O C3 H3O H

O O C3 H

H O C3 H O C H3

C H O m e t h o x y b e n z e n e s u 2 - m e t h o x y b e n l p h o n i c a c i d z e

(a)

(i) Name the reagent which converts methoxybenzene to 2methoxybenzene sulphonic acid. ...........................................................................................................................(1)

(ii)

Name the type of reaction which occurs and its mechanism. ...........................................................................................................................(2)


53

(b)

After the final stage, in which 2-methoxyphenol is converted to vanillin, the impure product can be purified by recrystallisation. In this process the solid is dissolved in the minimum volume of hot water. The mixture is then filtered whilst still hot. The filtrate is cooled in an ice bath to produce crystals of vanillin. These can be removed by filtration and dried. (i) Why is the minimum volume of hot water used? ........................................................................................................................... ...........................................................................................................................(1)

(ii)

The impure vanillin may contain soluble and insoluble impurities. Describe how each of these is removed during recrystallisation. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

How would you check the purity of the vanillin after recrystallisation, other than by using an infrared spectrometer. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


54

(c)

In order to establish whether or not vanillin had been formed, two infrared spectra were obtained: a sample of pure 2-methoxyphenol and a sample of the product. Study the spectra and data below. I n 1 8 T ra n s m itta n c e / % 6 4 2 0 0 0 0 0 3 0 0 0 W avenum ber/cm I n 1 T ra n s m itta n c e / % 8 6 4 0 0 0 0 3 0 0 0 W avenum ber/cm1 1

f r a r e d 0

S

p

e c t r u

m

o f

2 - M

e t h

o x y p

h

e n

o

2

0

0

0

f r a r e d 0

S

p

e c t r u

m

o f

P

r o d

u

c t

2

0

0

0

Wavenumber / cm C C Stretching Vibrations Arene Arene Alcohols and phenols Aldehydes Ketones Carboxylic acids Esters 1600 1450 3030 3750 3200 1740 1720 1700 1680 1725 1680 1750 1735 CH Stretching Vibrations OH Stretching Vibrations C O Stretching Vibrations

1


55

Comment as to whether any vanillin is likely to have been formed during the process. Support your answer with relevant evidence. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 10 marks)

36.

(a)

Give the electronic configuration of:

Cu : [Ar] ...................................................................................................................... Cu : [Ar] ......................................................................................................................(1)+

(b)

(i)

Explain why Cu ions are colourless.

+

........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


56

(ii)

Copper(I) ions disproportionate in aqueous solution. Give the equation for the reaction and use the standard electrode potentials given below to explain why the reaction occurs. E /V Cu (aq) + e + Cu (aq) + e2+

Cu (aq) Cu(s)

+

+ 0.15 + 0.52

........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

Explain why your answer to (ii) does not rule out the existence of Cu (aq) under standard conditions. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)

+

(c)

(i) When a small amount of dilute ammonia solution is added to a solution of copper(II) sulphate, a turquoise blue precipitate, F, is formed. F has the composition Cu 49.4%, S 12.5%, O 37.4%, H 0.78% by mass. Calculate its empirical formula.

(2)


57

(ii)

When F is dissolved in dilute hydrochloric acid, the resulting blue solution gives a white precipitate with barium chloride solution. Suggest a formula for F, given that all the hydrogen is present in hydroxide ions. ...........................................................................................................................(2)

(iii)

When excess concentrated ammonia is added to F, a deep blue solution is formed. Give the formula of the ion responsible for this colour. ...........................................................................................................................(1)

(iv)

What type of reaction is occurring in (iii)? ...........................................................................................................................(1)

(d)

Copper metal can be used as a catalyst. When propan-1-ol vapour is passed over heated copper, the following reaction occurs: CH3CH2CH2OH CH3CH2CHO + H2 (i) Outline how, by the use of 2,4-dinitrophenylhydrazine and suitable tables of data, you could show that the product is propanal. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(4)


58

(ii)

When propan-1-ol is oxidised with a solution of potassium dichromate(VI) in dilute sulphuric acid care must be taken to avoid further oxidation of the aldehyde product. How is this achieved? ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)

(iii)

What is the further oxidation product of the aldehyde? ...........................................................................................................................(1)

(iv)

Suggest why the oxidation of the alcohol by passing it over heated copper does not lead to further oxidation of the aldehyde. ........................................................................................................................... ...........................................................................................................................(1)

(v)

There are a few places on the surface of the metal where catalysis can occur. These are called active sites. Suggest why this leads to the rate of reaction being independent of the gas pressure unless this pressure is extremely low. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1) (Total 20 marks)


59

37.

Brass is a widely-used alloy that contains copper and zinc. There are many varieties of brass with different compositions. In the volumetric analysis of the composition of brass, the first step is to react a weighed sample of the alloy with nitric acid. This gives a greenish-blue solution. (a) The following standard electrode potentials are needed for this question: E /V Zn + 2e Zn 2+ Cu + 2e Cu + NO3 + 2H + e NO2 + H2O2+

0.76 + 0.34 + 0.81

(i)

Use the half equations given above and the values of E to calculate the standard electrode potential for the reaction between zinc and nitric acid and derive the equation. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Suggest why zinc does not produce hydrogen with nitric acid. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


60

(iii)

If the greenish-blue solution is diluted with water it turns light blue and contains hydrated copper(II) ions. Name the light blue complex ion and draw its structure so as to show its shape. Name ................................................................................................................. Structure:

(2)

(iv)

If concentrated hydrochloric acid is added to a portion of the light blue solution it turns green. State the type of reaction that occurs and give an equation for the reaction. ........................................................................................................................... ...........................................................................................................................(2)

(b)

The light blue solution from (a)(iii) is then neutralised, and reacted with an excess of potassium iodide solution. The following standard electrode potentials are needed: E /V + Cu + 0.15 2I + 0.54

Cu + e I2 + 2e

2+


61

(i)

Use these E values to explain why you would not expect the following reaction to occur. 2Cu (aq) + 4I (aq) 2CuI(s) + I2(aq) ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)2+

(ii)

Explain why, in practice, the reaction in (i) does occur and iodine is liberated. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

When the precipitate formed in the reaction in (i) is filtered off and then dissolved in concentrated aqueous ammonia, a colourless solution is produced. Suggest the formula of the cation in this solution. ...........................................................................................................................(1)

(iv)

If the colourless solution from (iii) is left to stand in air for some time, it turns blue. State why this is so, naming the reactant responsible for the change. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)


62

(c)

In a determination of the composition of a sample of brass, 1.50 g of the alloy was treated 3 to give 250 cm of a neutral solution of copper(II) nitrate and zinc nitrate. Excess potassium iodide solution was added to 25.0 cm portions of this solution, and the 3 liberated iodine titrated with 0.100 mol dm sodium thiosulphate solution. The mean titre 3 was 16.55 cm . 2Cu (aq) + 4I (aq) 2CuI(s) + I2(aq) 2S2O3 (aq) + I2(aq) 2I (aq) + S4O6 (aq)2 2 2+ 3

(i)

State which indicator you would use for the titration and the colour change seen at the end point. ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Explain why the indicator is not added until the reaction is nearly complete. ........................................................................................................................... ...........................................................................................................................(1)

(iii)

Calculate the percentage of copper by mass in this brass.



63

38.

This question concerns redox chemistry. Consider the following data E /V +0.77 +1.36 +1.51

Fe (aq) + e Cl2(aq) + 2e MnO4 (aq) + 8H (aq) + 5e +

3+

Fe (aq) 2Cl (aq) Mn (aq) + 4H2O(l)2+

2+

(a)

(i) Use the data to explain why dilute hydrochloric acid is not used to acidify solutions of potassium manganate(VII). ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Explain why titrations involving potassium manganate(VII) solution do not require the addition of an indicator. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)


64

(b)

(i) The ionic equation for the oxidation of iron(II) ions by manganate(VII) ions in acidic solution is MnO4 (aq) + 5Fe (aq) + 8H (aq) Mn (aq) + 4H2O(l) + 5Fe (aq) Explain, in terms of the half equations listed above, why the ratio of manganate(VII) ions to iron(ii) ions is 1 : 5 in this reaction. 2+ + 2+ 3+

(1)


65

(ii)

Patients suffering from iron deficiency are often prescribed tablets containing hydrated iron(II) sulphate, FeSO4.7H2O. Some tablets, of total mass 6.00 g, were dissolved in distilled water and made up to 3 3 200 cm in a volumetric flask. 25.0 cm portions of this solution were titrated 3 against a 0.0200 mol dm solution of acidified potassium manganate(VII). The 3 mean titre was 20.10 cm . Calculate the percentage of hydrated iron(II) sulphate in the tablets. [Molar mass FeSO4.7H2O = 278 g mol ]1

(5)

(c)

An important application of redox reactions is in car batteries. The electrolyte is aqueous sulphuric acid and the standard electrode potentials involved are shown below. E /V 0.13 +1.46

Pb (aq) + 2e + PbO2(s) + 4H (aq) + 2e

2+

Pb(s) 2+ Pb (aq) + 2H2O(l)

(i)

Calculate the standard e.m.f. of the cell. ........................................................................................................................... ...........................................................................................................................(1)


66

(ii)

A single cell in a car battery has an e.m.f. of 2.00 V. Suggest why this value is different from the answer calculated in (i). ........................................................................................................................... ...........................................................................................................................(1) (Total 11 marks)

39.

Air is drawn through 10.0 cm of an aqueous solution of vanadium(II) chloride of concentration 3 0.100 mol dm . The colour of the solution slowly changes as oxidation takes place. The air-oxidised solution is titrated with a solution of acidified potassium manganate(VII) of 3 3 concentration 0.0200 mol dm . The end point is found to be 20.0 cm . (i) Draw a diagram of suitable apparatus for carrying out the air-oxidation of the vanadium(II) chloride solution.

3

(1)

(ii)

Complete the half equation for acidified manganate(VII) ions acting as an oxidising agent. MnO4 (aq) + ..............H (aq) + 5e (aq) Mn (aq) + ..............H2O(1)(1) + 2+


67

(iii)

Calculate the number of moles of manganate(VII) ions used in the titration, and hence the number of moles of electrons removed by the manganate(VII) ions. Calculate the number of moles of vanadium(II) ions in the 10 cm of solution used. Find the oxidation number of vanadium in the air-oxidised solution given that vanadium(V) ions are formed in the titration.3

(4)

(iv)

Suggest ONE reason why acidified potassium manganate(VII) is a useful oxidising agent in redox titrations. ..................................................................................................................................... .....................................................................................................................................(1) (Total 7 marks)


68

40.

The element iodine can be produced from the mineral Chile saltpetre, which contains sodium iodate, NaIO3. The iodate ions are converted to iodine in a two-step process. Ionic equations for the reactions are shown below. Step 1 Step 2

IO3 (aq) + 3HSO3(aq) I (aq) + 3HSO4 (aq) IO3 (aq) + 5I (aq) + 6H (aq) 3I2(aq) + 3H2O(l) +

(a)

(i) Describe a test you could carry out to confirm the presence of iodide ions in a solution. Indicate the result of the test. Test ................................................................................................................... ........................................................................................................................... Result ................................................................................................................ ...........................................................................................................................(2)

(ii)

Identify the TWO elements in Step 1 which show a change of oxidation number during the reaction. Give their initial and final oxidation numbers. First element ........................................ ................................... Initial oxidation number ...................... number ..................... Final oxidation number ....................... number ...................... Second element Initial oxidation Final oxidation(3)

(iii)

The equation for Step 1 shows that 1 mole of iodate ions, IO3 , reacts with 3 moles of hydrogensulphite ions, HSO3. Show that your answers to (ii) agree with this ratio.(1)


69

(b)

An experiment was carried out to determine the concentration of the iodine prepared in Step 2 A 10.0 cm portion of the iodine solution was titrated with sodium thiosulphate solution 3 of concentration 0.0100 mol dm . The volume of sodium thiosulphate solution added at 3 the end-point was 24.0 cm . The equation for the reaction is I2(aq) + 2Na2S2O3(aq) 2NaI(aq) + Na2S4O6(aq)3

(i)

What piece of apparatus would you use to measure out the 10.0 cm portion? ...........................................................................................................................(1)

3

(ii)

Suggest a suitable indicator to show the end-point of this titration. State the colour change you would see. Indicator ................................................................................................................. From .........................................................to ........................................................(2)

(iii)

Calculate the number of moles of sodium thiosulphate used in the titration.

(1)


70

(iv)

Calculate the number of moles of iodine which reacted with the sodium thiosulphate solution.

(1)

(v)

Calculate the concentration, in mol dm , of the iodine solution.

3


41.

Paracetamol can be manufactured from phenol using the reaction sequence below. O HS t e p

O1

HS t e p 2

O

HS t e p

O3

H

N A B

2O

N C

2H

N P

H

C

3

O

C

H o l

a r a c e t a m


71

(a)

Give reagents and conditions for Step 1. ..................................................................................................................................... .....................................................................................................................................(2)

(b)

State the type of reaction that occurs in Step 2. .....................................................................................................................................(1)

(c)

(i)

Give the name of compound C.(1)

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

(ii)

Suggest a test and its results for the amino group in compound C. ........................................................................................................................... ........................................................................................................................... .....................................................

Documents

Unit Questions