f334 jun 07

ADVANCED GCE 2849/01CHEMISTRY (SALTERS)

Chemistry of Materials

MONDAY 18 JUNE 2007 Afternoon

Time: 1 hour 30 minutesCandidates answer on the question paper.Additional materials: Scientific calculator

Data Sheet for Chemistry (Salters) (Inserted)

This document consists of 19 printed pages, 1 blank page and a Data Sheet for Chemistry (Salters).

SPA (MML/CGW 13435 4/06) T24086/3 © OCR 2007 [R/100/3432] OCR is an exempt Charity [Turn over

INSTRUCTIONS TO CANDIDATES

• Write your name, Centre number and Candidate number in the boxes above.• Answer all the questions.• Use blue or black ink. Pencil may be used for graphs and diagrams only.• Read each question carefully and make sure you know what you have to do before starting your answer.• Do not write in the bar code.• Do not write outside the box bordering each page.• WRITE YOUR ANSWER TO EACH QUESTION IN THE SPACE PROVIDED. ANSWERS WRITTEN

ELSEWHERE WILL NOT BE MARKED.

INFORMATION FOR CANDIDATES

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

• You will be awarded marks for the quality of written communication where this is indicated in the question.

• You may use a scientific calculator.• A copy of the Data Sheet for Chemistry (Salters) is provided as an insert with

this question paper.• You are advised to show all the steps in any calculations.

FOR EXAMINER’S USE

Qu. Max. Mark

1 17

2 15

3 19

4 22

5 17

TOTAL 90

*CUP/T24086*

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Answer all the questions.

1 The smell and flavour of many white wines are due to the presence of an ester called a lactone.

The lactone shown below has a sweet coconut odour.

O

C

molecular formula C10H14O2

O

(a) Ring the part of the molecule that shows you that this lactone is an ester. [1]

(b) How many chiral carbons are present in the lactone molecule?

number of chiral carbons = ......................................................... [1]

(c) Thin layer chromatography (t.l.c.) can be used to show that this lactone is present in white wine.

However, the lactone is colourless.

Suggest one method of treating the t.l.c. plate to make the spot visible.

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

(d) The structure of the lactone can be identified by using mass spectrometry and nuclear magnetic resonance spectroscopy.

(i) In the mass spectrum of the lactone, at what mass value would you expect to see the molecular ion peak?

mass value = ......................................................... [1]

(ii) Also in the mass spectrum there is a peak at a mass value of 15.

Give the formula of the ion responsible for this peak.

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

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(iii) Two of the peaks in the n.m.r. spectrum of the lactone have chemical shifts of 1.0 and 1.6.

Identify the types of protons responsible for these peaks.

Give their relative intensities.

Use the space below for your rough working and enter your answers in the table below.

chemical shift (�)

type of proton relative intensity of peaks

1.0

1.6

[3]

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(e) A lactone can be synthesised by allowing a hydroxycarboxylic acid, A, to react intramolecularly.

This is shown in the equation below.

C

O

OH

OH

H2CH2O

H2CCH2

O

H2C

H2C

CH2

O+

A

C

(i) The formation of the lactone is catalysed by acid. Usually some concentrated sulphuric acid is added. When this acid is used the yield of the lactone is very much greater.

Suggest why this increase in yield occurs.

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

(ii) Under different conditions the hydroxycarboxylic acid forms a polymer instead of a lactone.

Draw the repeating unit of the polymer.

[2]

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(iii) Another hydroxycarboxylic acid, 3-hydroxybutanoic acid, forms compound C when treated with conc. H2SO4.

H3C HC

compound C

COOHCH

1. What type of reaction leads to the formation of the unsaturated compound?

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

2. Compound C exists as two stereoisomers.

Draw the structures of these isomers.

Explain why the two isomers of compound C are different.

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[Total: 17]

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2 Nickel-cadmium, Ni-Cd, cells are used in making the cheaper types of rechargeable batteries.

The electrolyte is potassium hydroxide.

(a) The standard electrode potentials, E , for the two half-reactions involved in the cell are given below.

half-reaction E / V

NiO2 + 2H2O + 2e– Ni(OH)2 + 2OH– +0.49

Cd(OH)2 + 2e– Cd + 2OH– +0.81

(i) Give the oxidation state of the nickel in NiO2.

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

(ii) Calculate the E cell value for a Ni-Cd cell operating under standard conditions.

Identify the positive electrode and explain your choice of answer in terms of electron movement in the cell.

E cell = ................................................................ V

positive electrode .................................................

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

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

(iii) Write the equation for the reaction which takes place when the cell is operating. State symbols are not required.

[2]

(iv) The standard electrode potential of an electrode can be measured using the standard hydrogen electrode. Give the conditions under which standard electrode potentials are measured.

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

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

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(b) Cadmium compounds are toxic, therefore Ni-Cd cells have to be effectively sealed. Nylon polymers are often used in cells to seal the two half-cells together.

A suitable nylon can be made by polymerising compound D.

C

compound D

O

NHH2C

CH2

H2C

H2C

CH2

In the polymerisation process, the ring is broken by hydrolysis and then the polymer is formed.

(i) Draw a line on compound D to indicate which bond is broken. [1]

(ii) Draw the structure for the repeating unit of the polymer formed.

[2]

(iii) Explain why the polymerisation of compound D proceeds without the loss or gain of water molecules.

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

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

(iv) One of the reasons nylon is useful as a sealant in batteries is that it has good strength properties.

Explain, in terms of intermolecular forces, why nylon is much stronger than poly(ethene).

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

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

[Total: 15]

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3 Amphetamines are a group of compounds which act as stimulants. Despite their side effects, which include anxiety and restlessness, they are still used in treating some sleeping disorders and also hyperactivity in children.

The formula of the simplest member of the group, amphetamine, is given below.

NH2

C6H5

(a) Amphetamine exists as two stereoisomers.

Draw three-dimensional structures to show these stereoisomers.

mirror

[2]

(b) Amphetamine is a colourless, oily liquid which is insoluble in water but dissolves in dilute sulphuric acid.

(i) Draw the structure for the organic ion formed when amphetamine reacts with acid.

[1]

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(ii) A white solid can be isolated from the amphetamine and sulphuric acid mixture.

Describe how this white solid can be purified by recrystallisation using a suitable solvent. In your answer describe a property that the solvent must have to make it ‘suitable’.

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(iii) The purified crystalline solid is used in most amphetamine-based medicines.

Suggest why the purified crystalline solid is used rather than amphetamine itself.

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

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(c) The leaves of a tree, Khat, found only in some parts of Africa and Arabia, contain compounds similar in structure to amphetamine. When eaten, fresh leaves have similar properties to amphetamine.

The structures of two of the compounds found in Khat leaves are shown below.

NH2

OH

cathine cathinone

NH2

O

(i) Give the names of the two functional groups, apart from the benzene ring, present in cathinone.

1 ........................................................................................................................................

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

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(ii) Part of the infra-red spectrum of one of these compounds is shown below.

Use this spectrum to identify which of the two compounds is present.

Show how you used this data.

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

(iii) Cathinone reacts with ethanoyl chloride in the ratio of 1 : 1.

Draw the structure of the organic product of this reaction.

[1]

A graph has been removed due to third party copyright restrictions

Details:

An infra-red spectrum of one of the compounds listed

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(d) In this question, one mark is available for the quality of spelling, punctuation and grammar.

Cathine is converted to cathinone by enzymic action.

Explain, in terms of enzyme action

• why only one stereoisomer of cathine is converted into cathinone • why enzyme reactions speed up as the temperature is increased but stop altogether

if the temperature is too high.

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Quality of Written Communication [1]

[Total: 19]

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PLEASE DO NOT WRITE ON THIS PAGE

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4 Paracetamol is one of the most common pain-killing drugs used in the UK. The graph opposite shows the rate at which it is removed from the body.

(a) (i) Use the graph to calculate the first and second half-lives for the removal of paracetamol.

On the graph show how you arrived at your answers.

first half-life = ......................................................... [3]

second half-life = ......................................................... [3]

(ii) Give the order of the process.

Explain your choice of answer.

order = ...................................

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

(iii) Give the rate equation for the breakdown of paracetamol in the body.

State the units for the rate constant.

rate equation .....................................................................................................................

units of rate constant ................................................................................................... [2]

(iv) A person takes two pain-killing tablets each containing 500 mg of paracetamol. The writing on the packet containing the tablets says that two more can be taken after four hours.

Use the graph to find out how much paracetamol is left in the body four hours after taking the first two tablets. Show how you arrived at your answer.

mass of paracetamol remaining in the body = ......................................................... [2]

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0 4000 8000 12 000 16 000 20 0002000 6000 10 000 14 000 18 0000.00

time / s

para

ceta

mol

/ g

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1.20

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(b) The formula of paracetamol is given below.

O C

N

H

OH

CH3

(i) Name the functional group that is circled.

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

(ii) A chemical test can be used to show the presence of this functional group in a solution of paracetamol.

Name the reagent and describe any observations.

reagent ..............................................................................................................................

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

(c) Paracetamol is easily hydrolysed by excess warm aqueous sodium hydroxide.

Draw the structural formulae of the organic products of the reaction.

[3]

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(d) Paracetamol gradually hydrolyses in the presence of water.

One of the organic products can easily be made into a soluble coloured compound.

(i) Describe how colorimetry can be used to measure the concentration of a coloured compound in solution.

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(ii) The concentration of the coloured compound can then be found at various time intervals during the reaction.

Describe how you would use a graph of concentration of the compound against time to measure the initial rate of the reaction.

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

[Total: 22]

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5 Blue-green crystals, a mixture of copper(II) ethanoate salts, were used by artists in the 15th–18th centuries as pigments in paints. These crystals form on copper and copper-containing alloys when the metal is left exposed to air under suitable conditions.

Copper plates were supported over vats containing boiling vinegar (ethanoic acid). In the process, copper is converted into a mixture of copper(I) and copper(II) oxides which then react to form copper(II) ethanoate.

(a) (i) Complete the electron configuration for a Cu atom.

1s2 2s2 2p6 .......................................................... [2]

(ii) State from which sub-shell the electron is lost when a Cu atom forms a Cu(I) ion.

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

(iii) Give the formula of the ethanoate ion.

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

(b) Copper(II) ethanoate dissolves in water to form a brightly coloured blue-green solution. This was used to colour the seas in old maps.

Various shades of blue and green can be obtained by adding other chemicals to this solution.

(i) On diluting the solution with water a pale blue colour forms. The complex ion, [Cu(H2O)6]2+, is now present in the solution.

Draw a structure to show clearly the shape of this complex ion.

Indicate clearly the type of bonding involved.

[4]

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(ii) Addition of a small amount of ammonia solution to this pale blue solution causes a pale blue precipitate to form.

Write an ionic equation, including state symbols, for the precipitation reaction.

[2]

(iii) What would you see if an excess of ammonia was shaken with the blue precipitate?

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

(c) Explain why a blue solution looks blue.

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(d) Many old maps which have been coloured using the blue-green pigment have become discoloured with reddish brown stains. Chemists believe that one of the reasons for this is air pollution. Two common air pollutants are NO2 and SO2.

The table below contains some data for standard electrode potentials.

half-reaction E / V

SO42–(aq) + 4H+(aq) + 2e– SO2(aq) + 2H2O(l) +0.17

Cu2+(aq) + 2e– Cu(s) +0.34

NO3–(aq) + 2H+(aq) + e– NO2(aq) + H2O(l) +0.80

Use this data to explain how air pollution has caused a reddish brown stain to form.

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

[Total: 17]

END OF QUESTION PAPER

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Copyright Acknowledgements:

Q.3 Infra-red spectrum reproduced from http://www.aist.go.jp/RIODB/SDBS/cgi-bin/cre_index.cgi.

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

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

f334 jun 07

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