Cambridge A Level Chemistry 9701 — 2014 Oct/Nov Paper 2 · Variant 3

This document consists of 10 printed pages and 2 blank pages. [Turn over IB14 11_9701_23/3RP © UCLES 2014 *6698895364* 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 fl uid. 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 9701/23 Paper 2 Structured Questions AS Core October/November 2014 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

2 9701/23/O/N/14 © UCLES 2014 Answer all the questions in the spaces provided. 1 (a) Successive ionisation energies for the elements fl uorine, F, to bromine, Br, are shown on the graph. 12 000 10 000 8000 6000 4000 2000 0 1 2 3 electrons removed 4 5 ionisation energy / kJ mol–1 F Cl Br (i) Explain why the fi rst ionisation energies decrease down the group. … … … … [3] (ii) Explain why there is an increase in the successive ionisation energies of fl uorine. … … … [2]

3 9701/23/O/N/14 © UCLES 2014 [Turn over (b) Group VII is the only group in the Periodic Table containing elements in all three states of matter at room conditions. State and explain, in terms of intermolecular forces, the trend in the boiling points of the elements down Group VII. … … … … … … [4] (c) Compounds containing different halogen atoms covalently bonded together are called interhalogen compounds. (i) One interhalogen compound can be prepared by the reaction between iodine and fl uorine. This compound has Mr = 222 and the percentage composition by mass: F, 42.8; I, 57.2. Calculate the molecular formula of this interhalogen compound. molecular formula … [3] (ii) Another interhalogen compound has the formula ICl. Draw a ‘dot-and-cross’ diagram of a molecule of this compound, showing outer shell electrons only. Explain whether or not you would expect this molecule to be polar. … … … [2]

4 9701/23/O/N/14 © UCLES 2014 (d) Some reactions involving chlorine and its compounds are shown in the reaction scheme below. NaCl (aq) + W(aq) Cl 2(g) Y(g) cold NaOH(aq) hot NaOH(aq) H2(g) UV NaCl (aq) + X(aq) Z(s) Y(aq) AgNO3(aq) bubble into water (i) Give the formulae of W, X, Y and Z. W … X … Y … Z … [4] (ii) Write an equation for the reaction of chlorine with hot NaOH(aq). … [2] (iii) State the oxidation numbers of chlorine at the start and at the end of the reaction in (ii). … [2] (iv) Write an ionic equation for the reaction of Y with AgNO3(aq). Include state symbols. … [1] [Total: 23]

5 9701/23/O/N/14 © UCLES 2014 [Turn over Question 2 starts on the next page.

6 9701/23/O/N/14 © UCLES 2014 2 The Haber process for the manufacture of ammonia, NH3, was originally devised at the start of the 20th century and was developed into a full-scale industrial process by Carl Bosch in 1913. The key step in the process is the reversible reaction of nitrogen and hydrogen in the presence of an iron catalyst. N2(g) + 3H2(g) 2NH3(g) ∆H = –92 kJ mol–1 (a) The hydrogen for this reaction can be formed by reacting methane with steam, during which carbon monoxide is also produced. Write an equation for this reaction. … [1] (b) Use the Boltzmann distribution shown to explain why a catalyst increases the rate of this reaction. number of molecules kinetic energy … … … … [4] (c) Draw a three-dimensional diagram to show the shape of an ammonia molecule. Name this shape and state the bond angle. shape … bond angle … [3]

7 9701/23/O/N/14 © UCLES 2014 [Turn over (d) The Haber process is typically carried out at a temperature of 400 °C. (i) With reference to Le Chatelier’s Principle and reaction kinetics, state and explain one advantage and one disadvantage of using a higher temperature. … … … … … … [4] (ii) State the expression for the equilibrium constant, Kp, for the formation of ammonia from nitrogen and hydrogen in the Haber process. Kp = [1] (iii) 2.00 moles of nitrogen and 3.00 moles of hydrogen were put in a vessel and left to reach equilibrium. At equilibrium, the pressure was 2.00 × 107 Pa and the mixture contained 1.60 moles of ammonia. Calculate Kp. Include the units. Kp = … units = … [5] [Total: 18]

8 9701/23/O/N/14 © UCLES 2014 3 P, Q, R and S are structural isomers with the molecular formula C5H10. All four compounds readily decolourise bromine in the dark. P, R and S do not exhibit stereoisomerism but Q exists as a pair of geometrical (cis-trans) isomers. All four compounds react with hot concentrated, acidifi ed potassium manganate(VII) to produce a variety of products as shown in the table. compound products P CO2 and CH3CH2CH2CO2H Q CH3CO2H and CH3CH2CO2H R CO2 and T (C4H8O) S CH3CO2H and (CH3)2CO T reacts with 2,4-dinitrophenylhydrazine reagent, 2,4-DNPH, to form an orange crystalline product but does not react with Fehling’s reagent. (a) Give the structural formulae of P, Q, R, S and T. P … Q … R … S … T … [5] (b) (i) Explain what is meant by the term stereoisomerism. … … … [2]

9 9701/23/O/N/14 © UCLES 2014 [Turn over (ii) Draw the displayed formulae of the geometrical isomers of Q and name them both. name … name … [2] (c) Name the organic product of the reaction of T with sodium borohydride, NaBH4. … [1] [Total: 10]

10 9701/23/O/N/14 © UCLES 2014 4 A series of reactions based on propan-1-ol is shown. CH3CH2CH2OH U (C3H8O) V CH3CH2CO2H reaction 2 HBr steam catalyst reaction 1 reaction 3 CH3CH=CH2 (a) Suggest a suitable reagent and conditions for reaction 1. … [2] (b) (i) Write an equation for reaction 2, using [O] to represent the oxidising agent. … [1] (ii) Suggest a suitable reagent and conditions for reaction 2. … [2] (c) Give the structural formulae of U and V. U … V … [2] (d) Suggest a suitable reagent and conditions for reaction 3. … … [2] [Total: 9]

11 9701/23/O/N/14 BLANK PAGE © UCLES 2014

12 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. 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. 9701/23/O/N/14 © UCLES 2014 BLANK PAGE

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the October/November 2014 series 9701 CHEMISTRY 9701/23 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, 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 October/November 2014 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 – October/November 2014 9701 23 © Cambridge International Examinations 2014 Question Mark Scheme Marks Total 1 (a) (i) increasing distance of (outer/highest energy) electron(s) from nucleus OR increasing distance of outer/valence shell from nucleus increased shielding / screening (from inner shells) reduces attraction 1 1 1 [3] (ii) increasing cation charge / effective nuclear charge OR decreasing number of electrons compared with protons increase in attraction 1 1 [2] (b) (boiling point) increases (down the group) increasing number of electrons (in molecules) down group increasing strength of / more van der Waals’ forces (allow correct alternatives to van der Waals’ forces) so more energy needed to overcome (the forces) 1 1 1 1 [4] (c) (i) F I 42.8 57.2 19 127 2.253 0.450 0.450 0.450 5 1 / IF5 EF = MF or IF5= 222 1 1 1 [3]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9701 23 © Cambridge International Examinations 2014 (ii) (Yes) as electronegativities are different 1 1 [2] (d) (i) W = NaClO; X = NaClO3; Y = HCl; Z = AgCl 1 1 1 1 [4] (ii) 3Cl2 + 6NaOH
5NaCl + NaClO3 + 3H2O M1: correct species M2: balanced equation 1 1 [2] (iii) 0 to –1 (0 to) +5 1 1 [2] (iv) Ag+(aq) + Cl –(aq)
AgCl(s) [1] [23] Cl I x xx x x x x

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9701 23 © Cambridge International Examinations 2014 Question Mark Scheme Marks Total 2 (a) CH4 + H2O
CO + 3H2 1 [1] (b) Label on graph indicating catalysed and uncatalysed Ea OR statement Ea catalysed is lower (than Ea uncatalysed) owtte Reference to catalyst creating alternative mechanism / reaction pathway / route Idea that more molecules have sufficient energy (to react) so greater chance / frequency of successful collisions 1 1 1 1 [4] (c) angle = 107o shape = (trigonal) pyramid(al) 1 1 1 [3] (d) (i) Advantage = higher rate Greater Kinetic Energy / speed / collision frequency / proportion of successful collisions Disadvantage – reduced yield / less product / more reactants (Forward reaction) exothermic AND (hence in accordance with Le Chatelier’s Principle) equilibrium / reaction shifts left (to counteract increasing temp) ora 1 1 1 1 [4] (ii) 3 2 2 2 3 p pH pN pNH × = K 1 [1] N H H H

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9701 23 © Cambridge International Examinations 2014 (iii) N2(g) + 3H2(g) ⇋ 2NH3(g) 2 3 0 (–0.8) (–1.6×3/2) 1.2 0.6 1.60 xNH3 = 1.6/3.4 (= 0.471) xN2 = 1.2/3.4 (= 0.353) xH2 = 0.6/3.4 (= 0.176) Kp = 0.4712 × (2 × 107)2 = 2.88 × 10–13 Pa–2 0.353 × 2 × 107 × 0.1763 × (2 × 107)3 1 1 1+1 [5] [18]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9701 23 © Cambridge International Examinations 2014 Question Mark Scheme Marks Total 3 (a) P: CH3CH2CH2CH=CH2 Q: CH3CH2CH=CHCH3 R: CH3CH2C(CH3)=CH2 S: CH3CH=C(CH3)2 T: CH3CH2COCH3 1 1 1 1 1 [5] (b) (i) (Different molecules with the) same (molecular and) structural formula different arrangements of atoms (in space) 1 1 [2] (ii) 1 1 [2] (c) butan-2-ol 1 [1] [10] C C C C H H H H C H H H H H H trans-pent-2-ene C C C C H H H H C H H H H H H cis-pent-2-ene

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9701 23 © Cambridge International Examinations 2014 Question Mark Scheme Marks Total 4 (a) reagent = conc H2SO4 or conc H3PO4 conditions = heat OR pass vapour over hot Al2O3 “reagent” “conditions” 1 1 [2] (b) (i) C3H7OH + 2[O]
C2H5CO2H + H2O 1 [1] (ii) reagent = sodium / potassium dichromate or correct formula conditions = H+ / acidified and (heat under) reflux 1 1 [2] (c) U = CH3CH(OH)CH3 V = CH3CHBrCH3 OR U = CH3CH2CH2OH V = CH3CH2CH2Br 1 1 [2] (d) reagent = KOH / NaOH conditions = ethanol / alcohol AND Heat / reflux 1 1 [2] [9]