Cambridge A Level Chemistry 9701 — 2015 May/June Paper 2 · Variant 3

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 May/June 2015 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 9 printed pages and 3 blank pages. [Turn over IB15 06_9701_23/4RP © UCLES 2015 *4984712466*

2 9701/23/M/J/15 © UCLES 2015 Answer all the questions in the spaces provided. 1 Neon is a noble gas. (a) Complete the full electronic confi guration of neon. 1s2 … [1] (b) (i) Explain what is meant by the term fi rst ionisation energy. … … … [3] (ii) Explain why the fi rst ionisation energy of neon is greater than that of fl uorine. … … [2] (c) Neon has three stable isotopes. isotope mass number percentage abundance 1 9.25 2 20 90.48 3 21 0.27 (i) Defi ne the term relative atomic mass. … … [2] (ii) Use the relative atomic mass of neon, 20.2, to calculate the mass number of isotope 1. mass number = … [2]

3 9701/23/M/J/15 © UCLES 2015 [Turn over (d) A mixture of neon and argon has a mass of 0.275 g. The mixture was placed in a gas syringe at a temperature of 25 °C and a pressure of 100 kPa. Under these conditions the mixture was found to occupy a volume of 200 cm3. (i) Calculate the average Mr of the mixture. average Mr = … [2] (ii) Use your answer to (i) to calculate the percentage of neon in the mixture. Give your answer to three signifi cant fi gures. percentage of neon = … % [1] (e) Neon and argon can both be obtained by fractional distillation of liquid air as they have different boiling points. Neon has a boiling point of 27.3 K. The boiling point of argon is 87.4 K. (i) Name the force that has to be overcome in order to boil neon or argon and explain what causes it. … … … [3] (ii) Explain why argon has a higher boiling point than neon. … … … [2] [Total: 18]

4 9701/23/M/J/15 © UCLES 2015 2 The elements in Group II, and their compounds, show a variety of trends in their properties. (a) Magnesium, calcium and barium all react with cold water to form hydroxides. (i) Describe and explain the trend in reactivity of these three elements with cold water. … … … … … [3] (ii) Give the equation for the reaction of magnesium with cold water. … [1] (iii) Suggest why the water eventually turns cloudy during the reaction of magnesium with cold water. … … [1] (iv) Suggest the equation for the reaction of hot magnesium with steam. … [1] (b) The oxides of magnesium, calcium and barium all react with dilute nitric acid to form nitrates. (i) Give the equation for the reaction of magnesium oxide with nitric acid. … [1] (ii) State the trend in thermal stability of the nitrates of Group II. … … [1] (iii) Give the equation for the thermal decomposition of magnesium nitrate. … [1]

5 9701/23/M/J/15 © UCLES 2015 [Turn over (iv) Apart from lithium nitrate, the nitrates of the Group I elements decompose in a different way to those of the Group II elements. The equation for the thermal decomposition of potassium nitrate is 2KNO3 → 2KNO2 + O2 By identifying any changes in oxidation number, explain which element is reduced and which is oxidised in this decomposition. … … … … [3] (c) A refractory material is one that does not decompose or melt at very high temperatures. Over 50% of magnesium oxide production is for use as a refractory material. Explain why magnesium oxide has a very high melting point. … … … [2] (d) The word ‘lime’ is usually used to refer to a range of calcium-containing compounds that have a range of uses. (i) Write equations to show how calcium carbonate can be converted into calcium hydroxide by a two-step process. … … [2] A garden pond, with a total volume of 8000 dm3, has been contaminated in such a way that its pH has fallen to 4. This means that the concentration of hydrogen ions, H+, in the water is 1 × 10–4 mol dm–3. (ii) Write an ionic equation for the neutralisation reaction that occurs between hydrogen ions and carbonate ions, CO3 2–. … [1] (iii) Use your equation to calculate the mass of powdered calcium carbonate that would need to be added to the pond to neutralise the acidity. mass = … g [2] [Total: 19]

6 9701/23/M/J/15 © UCLES 2015 3 A, B, C, D, E and F are all structural isomers with the molecular formula C4H8O. (a) A, B and C all give an orange precipitate when treated with 2,4-DNPH but only A and B give a brick-red precipitate when warmed with Fehling’s solution. (i) Draw the skeletal formulae of A, B and C. A B C [3] (ii) Name the type of structural isomerism shown by A and B. … [1] (iii) State what you would see when a sample of A is warmed with Tollens’ reagent. … [1]

7 9701/23/M/J/15 © UCLES 2015 [Turn over (b) D, E and F all decolourise bromine and effervesce slowly with sodium metal. E shows geometrical isomerism. Only D has a branched chain. None of these isomers contains an oxygen atom bonded to a carbon atom involved in π bonding. None of these isomers contains a chiral centre. (i) Give the structures of D, E and F. Show the two stereoisomers of E and label the stereoisomerism shown. D E … E … F [5] (ii) Identify the gas produced during the reaction of each of these isomers with sodium metal. … [1] (c) Another compound, G, C3H6O, contains the same functional group as A. Give equations for the reactions of G with each of acidifi ed potassium dichromate(VI) and sodium tetrahydridoborate, NaBH4, using [O] or [H] as appropriate. (i) reaction with acidifi ed potassium dichromate(VI) C3H6O + … → … [1] (ii) reaction with NaBH4 C3H6O + … → … [1] [Total: 13]

8 9701/23/M/J/15 © UCLES 2015 4 The structure of H is shown. C C H CH2OH CH3 CH3 CH3 (a) H reacts with both cold, dilute, acidifi ed potassium manganate(VII) and with hot, concentrated, acidifi ed potassium manganate(VII). (i) Give the structure of the organic product of the reaction of H with cold, dilute, acidifi ed potassium manganate(VII). [1] (ii) Give the structures of the organic products of the reaction of H with hot, concentrated, acidifi ed potassium manganate(VII). [2] (b) (i) Complete the reaction scheme to show the mechanism of the reaction of H with bromine to form J. Include all necessary curly arrows, lone pairs and charges. C C CH2OH CH3 Br δ+ Br δ– CH3 CH3 C CH3 C J CH3 Br CH3 CH2OH Br [3]

9 9701/23/M/J/15 © UCLES 2015 [Turn over (ii) Explain the origin of the dipole on the bromine molecule. … … [1] J is formed as an equimolar mixture of isomers. (iii) State the type of isomerism shown by J. … [1] (iv) Draw the structures of the two isomers of J. [2] [Total: 10]

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12 9701/23/M/J/15 © UCLES 2015 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. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the May/June 2015 series 9701 CHEMISTRY 9701/23 Paper 2 (Structured Question AS Core), 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 May/June 2015 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 2015 9701 23 © Cambridge International Examinations 2015 Question Mark Scheme Mark Total 1 (a) (1s2)2s22p6 [1] [1] (b) (i) The amount of energy required/energy change when one electron is removed from each atom in one mol of gaseous atoms [1] [1] [1] [3] (ii) Greater nuclear charge/number of protons Same shielding/number of shells/energy level [1] [1] [2] (c) (i) mean/average mass of the isotopes/an atom(s) relative to 1/12 of the mass of an atom of 12C/on a scale where an atom of 12C is (exactly) 12 [1] [1] [2] (ii) ( ) ( ) ( ) 100 9.25 0.27 21 90.48 20 20.2 y + × + × = 22.133 9.25 1815.27 2020 = − y = 22 [1] [1] [2] (d) (i) r M mRT pV = 6 3 r 10 200 10 100 298 8.31 0.275 pV mRT M − × × × × × = = Mr = 34.05/34.1 [1] [1] [2] (ii) (Let % Ne = x so % Ar = 100-x) 34.05 100 x) 39.9(100 20.2x = + - % Ne = 29.7 [1] [1] 1 (e) (i) Van der Waal’s/London/dispersion Uneven electron distribution/temporary dipole Induced dipole-dipole attraction [1] [1] [1] [3] (ii) more electrons more polarisable/greater attraction/stronger IMFs [1] [1] [2] [18]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9701 23 © Cambridge International Examinations 2015 Question Mark Scheme Mark Total 2 (a) (i) Reactivity increases down the group OR reference to observations that indicate trend Outer electrons lost more easily down group Due to increased distance/shielding of outer electrons from nucleus [1] [1] [1] [3] (ii) Mg + 2H2O
Mg(OH)2 + H2 [1] [1] (iii) Magnesium hydroxide sparingly soluble/insoluble [1] [1] (iv) Mg + H2O
MgO + H2 [1] [1] (b) (i) MgO + 2HNO3
Mg(NO3)2 + H2O [1] [1] (ii) (thermal stability) increases down the group [1] [1] (iii) 2Mg(NO3)2
2MgO + 4NO2 + O2 [1] [1] (iv) N from (+)5 to (+)3 O from –2 to 0 N is reduced and O is oxidised [1] [1] [1] [3] (c) (Very) strong electrostatic attraction/ionic bond High charge (density) of cation and anion/Mg2+ and O2- [1] [1] [2] (d) (i) CaCO3
CaO + CO2 CaO + H2O
Ca(OH)2 [1] [1] [2] (ii) 2H+ + CO3 2–
CO2 + H2O [1] [1] (iii) 1 × 10–4 × 8000 = 0.8 mol H+ 2 0.8 × 100.1 = mass CaCO3 = 40 g [1] [1] [2] [19] 3 (a) (i) A/B = C = [1] [1] [1] [3] (ii) Chain [1] [1] (iii) Silver mirror/ppt/solid (black/grey) [1] [1] O O O

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9701 23 © Cambridge International Examinations 2015 C C CH3 C H3 CH2OH C H3 O H OH O C CH3 C OH O C O C H3 CH3 Question Mark Scheme Mark Total (b) (i) D CH2=C(CH3)CH2OH E C H3 C C CH2 H H OH trans OR E E C H3 C C H H CH2OH cis OR Z F H2C=CHCH2CH2OH [1] [1+1] [1] [1] [5] (ii) Hydrogen [1] [1] (c) (i) C3H6O + [O]
C3H6O2 [1] [1] (ii) C3H6O +2[H]
C3H8O [1] [1] [13] 4 (a) (i) [1] [1] (ii) [1] [1] [2]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9701 23 © Cambridge International Examinations 2015 C C CH3 C H3 CH2OH C H3 Br Br δ+ δ− C C CH3 C H3 CH2OH H Br Br C C+ CH3 C H3 CH2OH C H3 Br Br- Question Mark Scheme Mark Total (b) (i) M1 = 2 curly arrows M2 = intermediate ion M3 = Br with –ve charge, lone pair and curly arrow to C+ [1] [1] [1] [3] (ii) dipole is induced by proximity to C=C [1] [1] (iii) Optical [1] [1] (iv) C CH3 C H2 C Br OH Br CH3 C H3 C C H3 C H2 C Br OH C H3 CH3 Br [1+1] [2] [10]