Cambridge A Level Chemistry 9701 — 2016 May/June Paper 2 · Variant 2

READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. CHEMISTRY 9701/22 Paper 2 AS Level Structured Questions May/June 2016 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level This document consists of 11 printed pages and 1 blank page. [Turn over IB16 06_9701_22/6RP © UCLES 2016 *6897461207*

2 9701/22/M/J/16 © UCLES 2016 Answer all the questions in the spaces provided. 1 (a) Complete the table to show the composition and identity of some atoms and ions. name of element nucleon number atomic number number of protons number of neutrons number of electrons overall charge boron 10 5 … … … 0 nitrogen … … … 8 10 … … 208 82 82 … 80 … … … … 3 3 … +1 [4] (b) The fifth to eighth ionisation energies of three elements in the third period of the Periodic Table are given. The symbols used for reference are not the actual symbols of the elements. ionisation energies, kJ mol–1 fifth sixth seventh eighth X 7012 8496 27 107 31 671 Y 6542 9362 11 018 33 606 Z 7238 8781 11 996 13 842 (i) State and explain the group number of element Y. group number … explanation … … [1] (ii) State and explain the general trend in first ionisation energies across the third period. … … … [2] (iii) Complete the electronic configuration of element X. 1s2 … [1]

3 9701/22/M/J/16 © UCLES 2016 [Turn over (c) A sample of oxygen exists as a mixture of three isotopes. Information about two of these isotopes is given in the table. mass number 16 17 abundance 99.76% 0.04% (i) Calculate the abundance of the third isotope. abundance = … % [1] (ii) The relative atomic mass of this sample of oxygen is 16.0044. Calculate the mass number of the third isotope. You must show your working. mass number = … [2] [Total: 11]

4 9701/22/M/J/16 © UCLES 2016 2 The elements in Group 17, the halogens, and their compounds, show many similarities and trends in their properties. Some data are given for the elements fluorine to iodine. element bond energy / kJ mol–1 standard enthalpy change of atomisation, / kJ mol–1 boiling point of element / K boiling point of hydrogen halide / K fluorine, F–F 158 79 85 293 chlorine, Cl –Cl 242 121 238 188 bromine, Br–Br 193 112 332 206 iodine, I–I 151 107 457 238 (a) (i) Explain the meaning of the term standard enthalpy change of atomisation. … … … [3] (ii) For fluorine and chlorine, the enthalpy changes of atomisation are half the value of the bond energies. For bromine and iodine, the enthalpy changes of atomisation are much more than half the value of the bond energies. Suggest a reason for this difference. … … … [1] (iii) The standard enthalpy of formation of iodine monochloride, ICl, is –24.0 kJ mol–1. Use this information and the bond energies of iodine and chlorine to calculate the I–Cl bond energy. I–Cl bond energy = … kJ mol–1 [2]

5 9701/22/M/J/16 © UCLES 2016 [Turn over (b) (i) Explain the trend in the boiling points of the hydrogen halides, HCl, HBr and HI. … … … [2] (ii) Suggest why the hydrogen halide HF does not follow the trend in boiling points shown by HCl, HBr and HI. … … … [2] (c) In an experiment, two of the halogens are represented as P2 and Q2. P2 combines with hydrogen on heating to form HP, which can be easily broken down into its elements. A solution of HP in water reacts with aqueous silver ions to form a yellow precipitate that is insoluble in dilute aqueous ammonia. Q2 combines explosively with hydrogen in sunlight to form HQ, which is stable to heat. A solution of HQ in water reacts with aqueous silver ions to form a white precipitate that is soluble in dilute aqueous ammonia. (i) Identify the halogens P2 and Q2. P2 = … Q2 = … [1] (ii) HP readily decomposes into its elements when heated but HQ is stable to heat. Explain this with reference to bond energies. … … … [2] (iii) Write an equation for the thermal decomposition of HP. … [1]

6 9701/22/M/J/16 © UCLES 2016 (iv) Write ionic equations, including state symbols, for 1. the formation of the white precipitate on addition of aqueous silver ions to aqueous HQ, … 2. the subsequent dissolving of this precipitate in dilute aqueous ammonia. … [2] (d) Chlorine reacts directly with many elements to form chlorides. Three such compounds are MgCl 2, Al Cl 3 and SiCl 4. (i) State and explain the pattern shown by the formulae of these three chlorides. … … … [2] (ii) Write equations to show the behaviour of each of these chlorides when added to water. MgCl 2 … Al Cl 3 … SiCl 4 … [3] [Total: 21]

7 9701/22/M/J/16 © UCLES 2016 [Turn over 3 Acidified potassium dichromate(VI) can oxidise ethanedioic acid, H2C2O4. The relevant half-equations are shown. Cr2O7 2– + 14H+ + 6e– → 2Cr3+ + 7H2O H2C2O4 → 2CO2 + 2H+ + 2e– (a) State the overall equation for the reaction between acidified dichromate(VI) ions and ethanedioic acid. … [2] (b) In an experiment a 0.242 g sample of hydrated ethanedioic acid, H2C2O4.xH2O, was reacted with a 0.0200 mol dm–3 solution of acidified potassium dichromate(VI). 32.0 cm3 of the acidified potassium dichromate(VI) solution was required for complete oxidation of the ethanedioic acid. (i) Calculate the amount, in moles, of dichromate(VI) ions used to react with the sample of ethanedioic acid. amount = … mol [1] (ii) Calculate the amount, in moles, of ethanedioic acid in the sample. amount = … mol [1] (iii) Calculate the relative molecular mass, Mr, of the hydrated ethanedioic acid. Mr = … [1] (iv) Calculate the value of x in H2C2O4.xH2O. x = … [1] [Total: 6]

8 9701/22/M/J/16 © UCLES 2016 4 This question is about molecules with molecular formula C4H8O2. (a) Give the structural formulae of the pair of chain isomers with the formula C4H8O2 that are carboxylic acids. [2] (b) (i) Give the structural formulae of a pair of positional isomers with the formula C4H8O2 that are esters. [2] (ii) Give the reagents and conditions needed to produce one of your esters in (i). … … [2]

9 9701/22/M/J/16 © UCLES 2016 [Turn over (c) The infra-red spectra of one of the esters and of another isomer, X, are shown. X decolourises bromine water and is not an ester or an acid. 100 50 0 transmittance 4000 3000 2000 wavenumber / cm–1 1500 1000 500 100 50 0 transmittance 4000 3000 2000 wavenumber / cm–1 infra-red spectrum of the ester infra-red spectrum of X 1500 1000 500 Explain the differences between these two spectra, with particular reference to the peaks with wavenumbers above 1500 cm–1. … … … … [3] [Total: 9]

10 9701/22/M/J/16 © UCLES 2016 5 A reaction sequence based on propan-1-ol is shown. CH3CH CH2 CH3CH2CH2 CH3CH2CH2 OH Br CH3CH2C OH O CH3CH2C H O CH3CH2C CN H OH reaction 1 reaction 4 propan-1-ol reaction 5 NaCN / H+ reaction 3 reaction 2 (a) Reactions 1 and 2 can both be carried out using the same reagents. (i) Identify suitable reagents for reactions 1 and 2. … … [1] (ii) State and explain how the reaction should be carried out to ensure that reaction 2 rather than reaction 1 occurs. … … … … [2] (b) Identify the necessary reagents and conditions for each of reactions 3 and 4. reaction 3 … … reaction 4 … … [2]

11 9701/22/M/J/16 © UCLES 2016 [Turn over (c) (i) Complete the reaction mechanism for reaction 5. Include all relevant lone pairs, curly arrows, charges and partial charges. CH3CH2 C CH3CH2 CN H OH O C H NC− [4] The product of reaction 5 exhibits stereoisomerism. (ii) Draw the two stereoisomers in the conventional way. [2] (iii) Suggest why a mixture of the two stereoisomers is formed by reaction 5. … … … [2] [Total: 13]

12 9701/22/M/J/16 © UCLES 2016 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. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. 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.

® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 7 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/22 Paper 2 AS Level Structured Questions May/June 2016 MARK SCHEME Maximum Mark: 60 Published 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, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2016 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total 1 (a) name of element nucleon number atomic number number of protons number of neutrons number of electrons overall charge boron 10 5 5 5 5 0 nitrogen 15 7 7 8 10 –3 lead 208 82 82 126 80 +2 lithium 6 3 3 3 2 +1 [1] [1] [1] [1] [4] (b) (i) Group 17 / VII / 7 AND big (owtte) increase / big difference / big gap / big jump / jump in increase / jump in difference after 7th IE [1] [1] (ii) increases across period due to increasing attraction (of nucleus for electrons) due to increasing nuclear charge / atomic / proton number AND constant / similar shielding / same (outer) shell / energy level [1] [1] [2] (iii) 1s22s22p63s23p4 [1] [1] (c) (i) (100 − 99.76 − 0.04=) 0.2 [1] [1] (ii) 0.2x + (99.76 × 16) + (0.04 × 17) = 16.0044 100 x = 18 [1] [1] [2] [Total 11]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total 2 (a) (i) enthalpy / energy / heat change when one mole of gaseous atoms is produced from the element in its standard state under standard conditions [1] [1] [1] [3] (ii) fluorine and chlorine are gases / bromine liquid and iodine solid OR as ∆Hat for bromine / iodine also includes changes of state [1] [1] (iii) (½Cl2 + ½I2 → ICl) ∆Hf = (½E(Cl2) + ½E(I2)) – E(ICl) OR E(ICl) = (151 / 2) + (242 / 2) + 24 E(ICl) = (+) 220.5 / 221 [1] [1] [2] (b) (i) stronger / more / greater id–id / London / dispersion forces due to increasing numbers of electrons [1] [1] [2] (ii) (intermolecular forces in HF are) hydrogen bonds (which are) stronger (than vdW) / more energy needed to separate molecules OR HF much more polar / F much more electronegative Intermolecular forces in HF stronger (than in HCl, HBr, HI) [1] [1] [1] [1] [2] (c) (i) P = iodine / I2 /I; Q = chlorine / Cl2 / Cl [1] [1] (ii) weaker H–P than H–Q bond ORA / easier /less energy to break H–P than H–Q ORA due to greater distance / shielding of nucleus from bond pair ORA [1] [1] [2]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total (iii) 2HP (or 2HI) → (or ⇌) H2 + P2 (or I2) [1] [1] (iv) Ag+(aq) + Q−(aq) (or Cl −) →AgQ(s) (or AgCl(s)) AgQ(s) / AgCl(s) + 2NH3(aq) → Ag(NH3)2 +(aq) + Q−(aq) / Cl –(aq) [1] [1] [2] (d) (i) no of Cl increases by one each time / matches group number due to increasing number of valence/outer(most/shell) electrons / oxidation number / valency (of Mg, Al , Si) [1] [1] [2] (ii) MgCl2 (+aq) → Mg2+ + 2Cl – AlCl3 + 6H2O → Al(H2O)6 3+ + 3Cl – / Al(H2O)5(OH)2+ + H+ + 3Cl – SiCl4 + 2H2O → SiO2 + 4H+ + 4Cl – [1] [1] [1] [3] [Total 21] 3 (a) Cr2O7 2− + 8H+ + 3H2C2O4 → 2Cr3+ + 6CO2 + 7H2O M1 = species M2 = balancing [1] [1] [2] (b) (i) (0.02 × 32.0/1000 =) 6.40 × 10−4 [1] [1] (ii) (6.4 × 10−4 × 3 = )1.92 × 10−3 [1] [1] (iii) (0.242 / 1.92 × 10−3 =) 126(.0) [1] [1] (iv) (126 – 90 = 36; 36 / 18 = 2 hence) x = 2 [1] [1] [Total 6]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total 4 (a) CH3CH2CH2COOH (CH3)2CHCOOH / CH3CH(CH3)COOH [1] [1] [2] (b) (i) Two from 1. CH3CH2COOCH3 2. CH3COOCH2CH3 3.HCOOCH2CH2CH3 [1] [1] [2] (ii) correct acid + alcohol for either ester 1. methanol + propanoic acid 2. ethanol + ethanoic acid 3. propan-1-ol + methanoic acid (conc)H2SO4 / (conc)H3PO4 AND heat / warm / reflux [1] [1] [2] (c) Peak at 1710–1750 (for ester) due to C(=)O Peak at 1500–1680 (for X) due to C(=)C / alkene Peak at 3200–3650 (for X) due to (alcohol) O(–)H [1] [1] [1] [3] [Total 9] 5 (a) (i) acidified / H+ AND potassium / sodium dichromate [1] [1] (ii) distillation (rather than reflux) (ensures aldehyde escapes) to avoid further oxidation / to avoid forming acid / as reflux causes further oxidation [1] [1] [2]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total (b) reaction 3 – (conc) H2SO4 / (conc) H3PO4 or Al 2O3 / pumice / porcelain / porous pot / ceramic AND heat reaction 4 – KBr / NaBr with (conc) H2SO4 or (red)P and Br2 / PBr3 AND heat [1] [1] [2] (c) (i) CH3CH2 C O H N C - H + CH3CH2 C OH H CN δ+ δ− CH3CH2 C O - H CN M1 = lone pair on C of CN– AND curly arrow from lone pair to carbonyl carbon M2 = dipole on C=O AND curly arrow to O from = M3 = intermediate with negative charge M4 = lone pair and curly arrow to H+ [1] [1] [1] [1] [4] (ii) CH3CH2 C OH H CN CH3 CH2 C OH H C N [1+1] [2]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 22 © Cambridge International Examinations 2016 Question Answer Mark Total (iii) attack / attach from either side / above or below / from two directions because the carbonyl / molecule is planar / trigonal / flat / because of the shape of the molecule OR product is chiral / has a chiral carbon / has a carbon attached to four different groups / has a chiral centre / is asymmetric (equal) chance of forming either (of the two optical isomers) / mechanism doesn’t distinguish between the two (optical isomers) / able to form either / chance of forming / able to form 50:50 OR because the carbonyl / molecule is planar / trigonal / flat OR because of the shape of the molecule (equal) chance of forming either (of the two optical isomers) / mechanism doesn’t distinguish between the two (optical isomers) / able to form either / chance of forming / able to form 50:50 [1] [1] [2] [Total 13]