Cambridge A Level Chemistry 9701 — 2008 May/June Paper 2 · Variant 1

This document consists of 10 printed pages and 2 blank pages. SP (SLM/CGW) T58865/2 © UCLES 2008 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level READ THESE INSTRUCTIONS FIRST Write your name, Centre number and candidate number on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs, or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. DO NOT WRITE IN THE GREY AREAS BETWEEN THE PAGES. * 8 5 2 2 4 4 3 8 7 8 * CHEMISTRY 9701/02 Paper 2 AS Structured Questions May/June 2008 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet For Examiner’s Use 1 2 3 4 5 Total

2 9701/02/M/J/08 © UCLES 2008 For Examiner’s Use Answer all the questions in the spaces provided. 1 The structural formulae of water, methanol and methoxymethane, CH3OCH3, are given below. O H H O H3C H O H3C CH3 (a) (i) How many lone pairs of electrons are there around the oxygen atom in methoxymethane? … (ii) Suggest the size of the C–O–C bond angle in methoxymethane. … [2] The physical properties of a covalent compound, such as its melting point, boiling point, vapour pressure, or solubility, are related to the strength of attractive forces between the molecules of that compound. These relatively weak attractive forces are called intermolecular forces. They differ in their strength and include the following. A interactions involving permanent dipoles B interactions involving temporary or induced dipoles C hydrogen bonds (b) By using the letters A, B, or C, state the strongest intermolecular force present in each of the following compounds. For each compound, write the answer on the dotted line. ethanal CH3CHO … ethanol CH3CH2OH … methoxymethane CH3OCH3 … 2-methylpropane (CH3)2CHCH3 … [4]

3 9701/02/M/J/08 © UCLES 2008 [Turn over For Examiner’s Use (c) Methanol and water are completely soluble in each other. (i) Which intermolecular force exists between methanol molecules and water molecules that makes these two liquids soluble in each other? … (ii) Draw a diagram that clearly shows this intermolecular force. Your diagram should show any lone pairs or dipoles present on either molecule that you consider to be important. [4] (d) When equal volumes of ethoxyethane, C2H5OC2H5, and water are mixed, shaken, and then allowed to stand, two layers are formed. Suggest why ethoxyethane does not fully dissolve in water. Explain your answer. … … … …[2] [Total: 12]

4 9701/02/M/J/08 © UCLES 2008 For Examiner’s Use 2 The Periodic Table we currently use is derived directly from that proposed by Mendeleev in 1869 after he had noticed patterns in the chemical properties of the elements he had studied. The diagram below shows the first ionisation energies of the first 18 elements of the Periodic Table as we know it today. 2500 He H Ne Li Na Ar 2000 1500 1000 500 2 4 6 8 10 1 3 5 7 12 14 17 9 proton number first ionisation energy /kJ mol-1 11 13 15 16 18 0 (a) Give the equation, including state symbols, for the first ionisation energy of fluorine. …[2] (b) Explain why there is a general increase in first ionisation energies from sodium to argon. … … … …[3] (c) (i) Explain why the first ionisation energy of aluminium is less than that of magnesium. … … …

5 9701/02/M/J/08 © UCLES 2008 [Turn over For Examiner’s Use (ii) Explain why the first ionisation energy of sulphur is less than that of phosphorus. … … … [4] The table below refers to the elements sodium to sulphur and is incomplete. element Na Mg Al Si P S melting point high conductivity high (d) (i) Complete the ‘melting point’ row by using only the words ‘high’ or ‘low’. (ii) Complete the ‘conductivity’ row by using only the words ‘high’, ‘moderate’ or ‘low’. [5] (e) When Mendeleev published his Periodic Table, the elements helium, neon and argon were not included. Suggest a reason for this. … …[1] [Total: 15]

6 9701/02/M/J/08 © UCLES 2008 For Examiner’s Use 3 When hydrocarbons such as petrol or paraffin wax are burned in an excess of air in a laboratory, carbon dioxide and water are the only products. When petrol is burned in a car engine, nitrogen monoxide, NO, is also formed. (a) Explain how NO is formed in an internal combustion engine but not formed when a small sample of petrol is burnt in an evaporating basin. … … …[2] The engines of modern motor cars have exhaust systems which are fitted with catalytic converters in order to reduce atmospheric pollution from substances such as NO. (b) (i) State three more pollutants, other than CO2 and H2O, that are present in the exhaust gases of a car engine. … and … and … (ii) What is the active material present in the catalytic converter? … (iii) Write one balanced equation to show how NO is removed from the exhaust gases of a car engine by a catalytic converter. … [4] NO is also formed when nitrosyl chloride, NOCl, dissociates according to the following equation. 2NOCl (g) 2NO(g) + Cl2(g) Different amounts of the three gases were placed in a closed container and allowed to come to equilibrium at 230 °C. The experiment was repeated at 465 °C. The equilibrium concentrations of the three gases at each temperature are given in the table below. concentration / mol dm–3 temperature / °C NOCl NO Cl 2 230 2.33 × 10–3 1.46 × 10–3 1.15 × 10–2 465 3.68 × 10–4 7.63 × 10–3 2.14 × 10–4

7 9701/02/M/J/08 © UCLES 2008 [Turn over For Examiner’s Use (c) (i) Write the expression for the equilibrium constant, Kc , for this reaction. Give the units. (ii) Calculate the value of Kc at each of the temperatures given. 230 °C 465 °C (iii) Is the forward reaction endothermic or exothermic? Explain your answer. … … [5] (d) The temperature of the equilibrium was then altered so that the equilibrium concentrations of NOCl and NO were the same as each other. What will be the effect on the equilibrium concentration of NOCl when the following changes are carried out on this new equilibrium? In each case, explain your answer. (i) The pressure of the system is halved at constant temperature. … … (ii) A mixture of NOCl(g) and NO(g) containing equal numbers of moles of each gas is introduced into the container at constant temperature. … … [4] [Total: 15]

9 9701/02/M/J/08 © UCLES 2008 [Turn over For Examiner’s Use 4 Two types of isomerism found in organic compounds are structural isomerism and cis-trans isomerism. (a) Draw displayed formulae for (i) two structural isomers of C2H4Br2, D E (ii) the cis- and the trans- isomers of C2H2Br2. cis trans [4] (b) (i) The cis- isomer of C2H2Br2 can be converted into one of the structural isomers of C2H4Br2. State the reagent(s) and conditions you would use to do this. … … (ii) Which of your structural isomers, D or E, would be formed? Explain your answer. isomer formed is … reason … [3] [Total: 7]

10 9701/02/M/J/08 © UCLES 2008 For Examiner’s Use 5 Ethanedial (glyoxal) is used in the production of fabrics which have permanent creases. O O C H ethanedial C H Ethanedial undergoes many of the reactions of aldehydes. (a) Ethanedial reacts with Tollens’ reagent. (i) What would you see if you carried out this reaction? … (ii) What is the structural formula of the organic compound formed? [2] (b) Ethanedial reacts with hydrogen cyanide, HCN, to give compound F. (i) What is the structural formula of F? (ii) What type of reaction is this? … (iii) What is the structural formula of the compound formed when F is heated with an aqueous mineral acid such as dilute sulphuric acid? [3]

11 9701/02/M/J/08 © UCLES 2008 For Examiner’s Use (c) Ethanedial can be oxidised and reduced. (i) What is the structural formula of the organic compound formed when ethanedial is heated under reflux with an excess of acidified potassium dichromate(VI)? (ii) What is the structural formula of the compound formed when ethanedial is reduced? (iii) What reagent would be used for this reduction? … [3] (d) When ethanedial is reacted with NaOH and the product treated with a mineral acid such as dilute sulphuric acid, the following reaction sequence takes place. I CHOCHO + NaOH → HOCH2CO2Na II HOCH2CO2Na + H+ → HOCH2CO2H + Na+ What type of reaction is the overall change? …[1] (e) An isomer of ethanedial exists which reacts with sodium metal to give hydrogen. Suggest the displayed formula of this isomer. [2] [Total: 11]

12 9701/02/M/J/08 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2008 question paper 9701 CHEMISTRY 9701/02 Paper 2 (AS Structured Questions), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2008 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9701 02 © UCLES 2008 1 (a) (i) 2 (1) (ii) between 104° and 105° (1) [2] (b) ethanal CH3CHO A (1) ethanol CH3CH2OH C (1) methoxymethane CH3OCH3 A (1) 2-methylpropane (CH3)2CHCH3 B (1) [4] (c) (i) hydrogen bonds (1) (ii) correct dipole on an -OH bond (1) hydrogen bond shown between the lone pair of an O and a H atom in an –OH group (1) lone pair on O atom of CH3OH or H2O clearly shown in the hydrogen bond (1) e.g. CH3  : O : LLHOH  H or H  : O : LLHOCH3  H [4] (d) hydrogen bonds exist between H2O molecules (1) hydrogen bonds cannot form between C2H5OC2H5 molecules (1) [2] [Total: 12]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9701 02 © UCLES 2008 2 (a) F(g) → F+(g) + e– correct equation (1) correct state symbols (1) [2] (b) from Na to Ar, electrons are added to the same shell/have same shielding (1) are subject to increasing nuclear charge/proton number (1) are closer to the nucleus or atom gets smaller (1) [3] (c) (i) Al and Mg in Al outermost electron is in 3p rather than 3s (1) 3p electron is at higher energy or is further away/is more shielded from nucleus (1) (ii) P and S for P 3p sub-shell is singly filled and for S one 3p orbital has paired electrons (1) paired electrons repel (1) [4] (d) (i) and (ii) element Na Mg Al Si P S melting point low ------ high high low low conductivity high ------ high moderate low low (1) (1) (1) (1) (1) one mark for each correct column [5] (e) because they had not been discovered (1) [1] [Total: 15]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9701 02 © UCLES 2008 3 (a) high temperature (and/or pressure) provide enough energy (1) to break N≡N bond or to provide Ea for N2/O2 reaction (1) [2] (b) (i) two from C, CO, hydrocarbon, SO2, H2S, NO2/NOx (1 + 1) not CO2, H2, H2O, SO3, NO (ii) Pt or Pd or Pt/Rh or Pt/Pd/Rh (1) (iii) 2NO + 2CO → 2CO2 + N2 or 2NO + C → CO2 + N2 (1) [4] (c) (i) [ ] [ ] [ ] 2 2 2 c NOC C NO l l = K (1) units are mol dm–3 (1) (ii) at 230 °C 2 3 2 2 3 c ) 10 33 . 2 ( 10 15 . 1 ) 10 46 . 1 ( − − − × × × × = K = 4.5 × 10–3 mol dm–3 (1) at 465 °C 2 4 4 2 3 c ) 10 68 . 3 ( 10 14 . 2 ) 10 63 . 7 ( − − − × × × × = K = 9.2 × 10–2 mol dm–3 (1) allow ecf on answer to part (i) (iii) endothermic because Kc increases with temperature mark is for explanation allow ecf on answer to part (ii) (1) [5] (d) (i) equilibrium moves to RHS (1) more moles on RHS (1) (ii) no change to equilibrium position (1) [NOCl ] and [NO] change by same amount (1) [4] [Total: 15]

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9701 02 © UCLES 2008 4 (a) (i) H H   Br C  C  Br   H H D H Br   H C  C  Br   H H E (1) (1) (ii) Br Br C=C H H cis Br H C=C H Br trans (1) (1) [4] (b) (i) hydrogen (1) nickel catalyst – allow platinum or palladium (1) (ii) isomer formed must be 1,2-dibromoethane (D above) because cis isomer has one Br atom on each carbon atom (1) mark is for the reason but wrong isomer is penalised [3] [Total: 7]

Page 6 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9701 02 © UCLES 2008 5 (a) (i) silver or black ppt. (1) (ii) O=C—C=O or HO2CCO2H (1)   HO OH allow anion [2] (b) (i) NC CN or NCCH(OH)CH(OH)CN (1)   HO—C—C—OH allow NCCH(OH)CHO   H H (ii) nucleophilic addition (1) (iii) HO2C CO2H or HO2CCH(OH)CH(OH)CO2H (1)   HO—C—C—OH allow HO2CCH(OH)CHO (ecf)   H H [3] (c) (i) O=C—C=O or HO2CCO2H (1)   HO OH (ii) H H or HOH2CCH2OH (1)   HO—C—C—OH allow HOH2CCHO   H H (iii) NaBH4 or LiAl H4 or H2/Ni (1) [3] (d) both oxidation and reduction allow disproportionation (1) [1] (e) HO—C≡C—OH – candidate’s compound must be C2H2O2 -OH present (1) C≡C present (1) [2] [Total: 11]