Cambridge A Level Chemistry 9701 — 2016 Oct/Nov 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 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 9701/23 Paper 2 AS Level Structured Questions October/November 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 10 printed pages and 2 blank pages. [Turn over IB16 11_9701_23/RP R © UCLES 2016 *0537133563*

2 9701/23/O/N/16 © UCLES 2016 Answer all the questions in the spaces provided. 1 A 0.17 g sample of a Group 14 chloride, XCl 4, reacted with water to produce an oxide, XO2, and HCl. equation 1 XCl 4(s) + 2H2O(l) → XO2(s) + 4HCl (aq) The HCl produced was absorbed in 100 cm3 of 0.10 mol dm–3 sodium hydroxide solution (an excess). In a titration, the unreacted sodium hydroxide solution required 30.0 cm3 of 0.20 mol dm–3 hydrochloric acid for complete neutralisation. (a) Calculate the amount, in moles, of hydrochloric acid used in the titration to neutralise the unreacted sodium hydroxide solution. amount = … mol [1] (b) Write the equation for the reaction between hydrochloric acid and sodium hydroxide. … [1] (c) Calculate the amount, in moles, of sodium hydroxide neutralised in the titration. amount = … mol [1] (d) Calculate the amount, in moles, of sodium hydroxide that reacted with the HCl produced by the reaction in equation 1. amount = … mol [1] (e) Calculate the amount, in moles, of HCl produced by the reaction in equation 1. amount = … mol [1]

3 9701/23/O/N/16 © UCLES 2016 [Turn over (f) Calculate the amount, in moles, of XCl 4 in the original 0.17 g sample. amount = … mol [1] (g) Calculate the molecular mass, Mr, of XCl 4. Mr = … [1] (h) Calculate the relative atomic mass, Ar, of X and suggest its identity. Ar of X = … identity of X … [2] [Total: 9]

4 9701/23/O/N/16 © UCLES 2016 2 For many compounds the enthalpy change of formation cannot be calculated directly. An indirect method based on enthalpy changes of combustion can be used. The enthalpy change of combustion can be found by a calorimetry experiment in which the heat energy given off during combustion is used to heat a known mass of water and the temperature change recorded. (a) (i) Explain the meaning of the term standard enthalpy change of combustion. … … … [3] (ii) Write the equation for the complete combustion of ethanol, C2H5OH. … [1] (b) In an experiment to determine the enthalpy change of combustion of ethanol, 0.23 g of ethanol was burned and the heat given off raised the temperature of 100 g of water by 16.3 °C. (i) Calculate the heat energy change, q, during the combustion of 0.23 g of ethanol. q = … J [1] (ii) Calculate the enthalpy change on burning 1 mole of ethanol. Include a sign in your answer. ∆H = … kJ mol–1 [1] (iii) Suggest two reasons why the value for the enthalpy change of combustion of ethanol determined by a simple laboratory calorimetry experiment is likely to be lower than the true value. … … … … [2]

5 9701/23/O/N/16 © UCLES 2016 [Turn over (c) The table gives some enthalpy change of combustion values. substance enthalpy change of combustion / kJ mol–1 C(s) –393.5 H2(g) –285.8 C3H7OH(l) –2021.0 (i) Construct a labelled energy cycle to show how these values could be used to calculate the enthalpy change of formation of C3H7OH(l), ∆Hf. 3C(s) + 4H2(g) + 1 2 O2(g) ∆Hf C3H7OH(l) [3] (ii) Calculate the enthalpy change of formation, ∆Hf, of C3H7OH(l). ∆Hf = … kJ mol–1 [2] [Total: 13]

6 9701/23/O/N/16 © UCLES 2016 3 The elements in Group 2 and their compounds show various trends in their physical and chemical properties. (a) The graph below shows the radius values of the atoms and 2+ ions of the elements in Group 2. 0.25 0.20 0.15 0.10 0.05 0 radius / nm Be Mg Ca Sr element Ba Ra (i) Explain why both lines show a steady increase in the values of the radii down the group. … … … [2] (ii) State and explain which line represents the atomic radii and which represents the ionic radii. … … … [2] (b) L is a salt of a Group 2 element M. When L is heated strongly a brown gas is observed and a white solid remains. The white solid dissolves in water to form a colourless solution of the metal hydroxide M(OH)2. Addition of dilute sulfuric acid to this colourless solution produces a dense white precipitate. (i) Identify the anion in salt L. … [1]

7 9701/23/O/N/16 © UCLES 2016 [Turn over (ii) Identify the element M and write an ionic equation for the formation of the white precipitate with sulfuric acid. M = … equation … [1] (iii) Give the formula of salt L and use it to write an equation for the thermal decomposition of salt L. formula of salt L … equation … [2] (c) Calcium carbonate and calcium hydroxide can both be used in agriculture to neutralise acidic soils. (i) Write ionic equations for the neutralisation of acid by each of calcium hydroxide and calcium carbonate. calcium hydroxide … calcium carbonate … [2] (ii) Suggest and explain why calcium carbonate is a better choice than calcium hydroxide for this purpose in areas of high rainfall. … … … [2] (d) Magnesium reacts with both cold water and steam. Give the formula of the magnesium-containing product of each of these reactions. with cold water … with steam … [2] [Total: 14]

8 9701/23/O/N/16 © UCLES 2016 4 In each section of this question an organic compound is shown. For each compound give its name and answer the questions about it. (a) CH3CH2CH(CH3)CH=CHCH3 (i) name … [1] (ii) This compound shows stereoisomerism. Define stereoisomerism. … … … [1] (iii) State and explain how many stereoisomers of this structure there are. … … … … … … [4] (b) (CH3)2C=C(CH3)2 (i) name … [1] (ii) Draw the skeletal formula of the organic product of the reaction of this compound with cold, dilute, acidified manganate(VII) ions. [1] (iii) Name the organic product of the reaction of this compound with hot, concentrated, acidified manganate(VII) ions. … [1] (iv) Draw the structure of part of a molecule of the addition polymer formed from this compound, showing exactly three repeat units. [1]

9 9701/23/O/N/16 © UCLES 2016 [Turn over (c) (CH3)2C=CH2 (i) name … [1] (ii) Complete the mechanism for the reaction of this compound with hydrogen bromide. Include all necessary curly arrows, lone pairs, charges and partial charges. H3C CH2 CH3 C H3C CH3 CH3 C Br H Br Br – 2-bromomethylpropane [4] (iii) Explain fully why 2-bromomethylpropane is the major product of this reaction while only relatively small amounts of 1-bromomethylpropane are produced. … … … … … … … [3] [Total: 18]

10 9701/23/O/N/16 © UCLES 2016 5 A sequence of reactions is shown starting with an alcohol, C3H7OH. CH3CH2CO2H C3H7OH CH3CH2CHO reaction 1 reaction 3 reaction 2 P (a) Draw the skeletal formula of the alcohol C3H7OH. [1] (b) State the reagents and conditions needed for reaction 1. … … [2] (c) State the reagents and conditions needed for reaction 2. … … [2] (d) Name P, the organic product of reaction 3. … [1] [Total: 6]

11 9701/23/O/N/16 © UCLES 2016 BLANK PAGE

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® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 8 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/23 Paper 2 AS Structured Questions October/November 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 October/November 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 – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 1(a) 6 × 10−3 (mol) 1 1 1(b) NaOH + HCl → NaCl + H2O 1 1 1(c) 6 × 10−3 (mol) 1 1 1(d) 4 × 10−3 (mol) 1 1 1(e) 4 × 10−3 (mol) 1 1 1(f) 1 × 10−3 (mol) 1 1 1(g) 170 1 1 1(h) 28(.0) Si/silicon 1 2 1 Total: 9

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 2(a)(i) Enthalpy / energy / heat change when one mole of a substance Burns / combusts / reacts in excess oxygen OR Completely burns / combusts / reacts in oxygen under standard conditions 1 3 1 1 2(a)(ii) C2H5OH + 3O2 → 2CO2 + 3H2O 1 1 2(b)(i) 6813.4 / 6813 / 6810 / 6800 (J) 1 1 2(b)(ii) –1362.68 / −1362.7 / –1363 / –1360 / –1400 (kJ) 1 1 2(b)(iii) Any 2 from: heat / energy losses (to air and/or to the container/surroundings) incomplete combustion (volatile) ethanol evaporated ethanol is impure not all energy is lost as heat 2 1 1 2(c)(i) 3 1+1 1

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 2(c)(ii) ∆Hf + (−2021.0) = 3(−393.5) + 4(−285.8) ∆Hf = −302.7 (kJ mol−1) 1 2 1 Total: 13 Question Answer Marks 3(a)(i) (Atoms/ ions become larger as) the number of (electron) shells increases (down the group) Increased distance of (outer) electrons (from the nucleus) OR Increased shielding results in weaker (nuclear) attraction / pull 1 2 1 3(a)(ii) top line / dotted line is atomic radii / bottom line / line with crosses is ionic radii (as atoms bigger than ions) Atom has one more shell (than corresponding ion) (ora) OR Atom loses two electrons / outer (shell) electrons / valency electrons (ora) OR Atom loses electrons and so (nuclear) attraction is stronger OR Nuclear charge in ion is greater than the electron(ic) charge (ora) OR Effective nuclear charge in ion is greater (ora) 1 2 1 3(b)(i) Nitrate / Nitrate(V) / NO3 − 1 1 3(b)(ii) Ba / barium OR Sr / Strontium Ba2+ + SO4 2− → BaSO4 OR Sr2+ + SO4 2− → SrSO4 1 1

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 3(b)(iii) Ba(NO3)2 OR Sr(NO3)2 2Ba(NO3)2 → 2BaO + 4NO2 + O2 OR 2Sr(NO3)2 → 2SrO + 4NO2 + O2 1 2 1 3(c)(i) H+ + OH− → H2O OR Ca(OH)2 + 2H+ → Ca2+ + 2H2O 2H+ + CO3 2− → CO2 + H2O OR CaCO3 + 2H+ → Ca2+ + CO2 + H2O OR H+ + CO3 2− → HCO3 – OR CaCO3 + H+ → Ca2+ + HCO3 – 1 2 1 3(c)(ii) Calcium carbonate is insoluble / less soluble (ora) Calcium carbonate is less likely to be / won’t get washed away (ora) OR Calcium carbonate lasts longer (ora) OR Calcium carbonate is less reactive / reacts more slowly (ora) 1 2 1 3(d) Mg(OH)2 MgO 1 2 1 Total: 14

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 4(a)(i) 4-methylhex-2-ene 1 1 4(a)(ii) (Molecules with the) same structural formula (and same molecular formula) with different arrangement of atoms/groups (in space) 1 1 4(a)(iii) 4 double-bond / alkene (2) different groups on each double-bonded carbon (one) chiral carbon (centre) / (one) carbon atom has 4 different groups attached / is asymmetric / is chiral 1 4 1 1 1 4(b)(i) 2,3-dimethylbut-2-ene 1 1 4(b)(ii) 1 1 4(b)(iii) Propanone 1 1 4(b)(iv) 1 1 4(c)(i) (2-)methylprop(-1-)ene 1 1

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 4(c)(ii) 4 4 4(c)(iii) (tertiary carbocat)ion / (tertiary) intermediate is / C+ with least number of hydrogen atoms bonded to it is more stable (than primary) due to (positive) inductive effect of three/more methyl groups (cf one) / three / more electron releasing methyl groups three / more electron donating methyl groups reducing charge (density) on C+ 1 3 1 1 Total: 18

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 23 © UCLES 2016 Question Answer Marks 5(a) 1 1 5(b) H+ / Cr2O7 2− (heat under) reflux 1 2 1 5(c) H+ / Cr2O7 2− (heat and) distil 1 2 1 5(d) (1-)propyl propanoate 1 1 Total: 6