Cambridge A Level Chemistry 9701 — 2016 May/June Paper 5 · 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. Use of a Data Booklet is unnecessary. 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 9701/52 Paper 5 Planning, Analysis and Evaluation May/June 2016 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. This document consists of 11 printed pages and 1 blank page. [Turn over IB16 06_9701_52/6RP © UCLES 2016 *4379664099* Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

2 9701/52/M/J/16 © UCLES 2016 1 A more reactive metal will displace a less reactive metal from a solution of its salt. This reaction is exothermic. If the same reaction is set up in an electrochemical cell then, instead of an enthalpy change, electrical energy is produced and a cell voltage can be measured. You are to plan an investigation of the reaction of three different metals (magnesium, iron and zinc) with aqueous copper(II) sulfate. You will plan to investigate whether there is a relationship between their cell potential values, , and their enthalpy changes of reaction, ∆Hr. Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s) Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s) Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Copper(II) sulfate solution is classified as a moderate hazard. Zinc sulfate solution is classified as corrosive. Iron(II) sulfate solution is classified as a health hazard. (a) Predict how ∆Hr may change as increases. Give a reason for your prediction. … … … [1] (b) The first part of the investigation is to determine the enthalpy change, ∆Hr, for the reaction of the same number of moles of three powdered metals with 0.500 mol dm–3 copper(II) sulfate. When determining the ∆Hr for the reaction of the metals listed above with aqueous copper(II) sulfate, the independent variable is, … … the dependent variable is. … … [2]

3 9701/52/M/J/16 © UCLES 2016 [Turn over You are provided with a sample of powdered metal and 50.0 cm3 of 0.500 mol dm–3 aqueous copper(II) sulfate. (c) (i) Draw a fully labelled diagram to show how the apparatus should be set up to allow you to determine the increase in temperature of aqueous copper(II) sulfate. You should use apparatus normally found in a school or college laboratory. [1] (ii) State the measurements you would make in your experiment. … … … [2] (iii) Other than eye protection, state one precaution you would take to make sure that the experiment proceeds safely. … … [1]

4 9701/52/M/J/16 © UCLES 2016 (iv) For the reaction with magnesium, calculate the mass of magnesium, in g, you would use so that it is in a small excess. You must show your working. [Ar: Mg, 24.3] mass of Mg = … g [2] (v) Explain why the metal used should be in powdered form rather than in strips. … … [1] (vi) The aqueous copper(II) sulfate and metal mixture should be stirred continuously. Explain why. … … [1] (d) In one experiment, the increase in temperature when excess magnesium powder is added to 50.0 cm3 of 0.500 mol dm–3 aqueous copper(II) sulfate is 58.5 °C. Calculate the enthalpy change for this reaction, ∆Hr, in kJ mol–1. Assume the specific heat capacity, c, of the reaction mixture is 4.18 J g–1 K–1. Assume 1.0 cm3 of 0.500 mol dm–3 aqueous copper(II) sulfate has a mass of 1.0 g. Include a sign in your answer. Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s) ∆Hr = … kJ mol–1 [2]

5 9701/52/M/J/16 © UCLES 2016 [Turn over (e) The second part of the investigation involves determining the cell potential, , for the three electrochemical cells. cell reaction Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s) Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s) Draw a diagram of the apparatus you would use to measure the for the magnesium/copper cell. Your labels should include the names of the metals and the names and concentrations of the solutions you would use. [3] (f) Explain why the enthalpy change determination and cell potential determination should be carried out at the same temperature as each other. … … … [1]

6 9701/52/M/J/16 © UCLES 2016 (g) Accepted values are shown for the cell reactions. cell reaction / V ∆Hr 1 Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s) +2.72 2 Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) +1.10 3 Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s) +0.78 Use your prediction in (a), your answer to (d) and data from the table to predict ∆Hr values for reactions 2 and 3. Complete the table with these values. [1] [Total: 18]

7 9701/52/M/J/16 © UCLES 2016 [Turn over 2 The relative molecular mass, Mr, of volatile liquids can be determined using the apparatus below. steam in steam out gas syringe steam jacket self-sealing cap hypodermic syringe volatile liquid thermometer A known mass of volatile liquid is injected into the gas syringe using a hypodermic syringe. The injected volatile liquid vaporises and the volume of vapour is recorded. The experiment can be repeated using different samples of the same volatile liquid. The following mathematical relationship can be used to calculate the relative molecular mass if the experiment is carried out at 100 °C and 1.01 × 105 Pa. V = 3.07 × 104 × m Mr m is the mass of the volatile liquid in g. V is the volume of the volatile liquid in cm3 when vaporised. A graph of V against m can be plotted. A group of students is given a volatile liquid hydrocarbon, Y, and asked to find its relative molecular mass in a series of experiments using this procedure. • A 100 cm3 gas syringe is placed in a steam jacket. • Approximately 5 cm3 of air is pulled into the gas syringe. • The temperature is allowed to reach a constant 100 °C. • Once the air in the gas syringe has stopped expanding, its volume is recorded. • The hypodermic syringe is filled with liquid Y. • The total mass of the hypodermic syringe and liquid Y is recorded. • A little liquid Y is injected into the hot gas syringe. • The total mass of the hypodermic syringe is recorded again. • The maximum volume of air and vapour in the gas syringe is recorded. • The mass of liquid Y injected into the gas syringe is calculated and recorded.

8 9701/52/M/J/16 © UCLES 2016 The results from the group of students are given in the table. mass of syringe + liquid Y before injection / g mass of syringe + liquid Y after injection / g volume of air in gas syringe before injection / cm3 volume of air + vapour Y in gas syringe after injection / cm3 mass of liquid Y used / g volume of vapour Y / cm3 4.83 4.68 7 55 5.33 5.23 9 44 4.85 4.64 13 85 5.09 4.92 11 69 5.31 5.07 14 97 5.57 5.48 8 39 5.32 5.12 9 79 5.17 4.94 12 91 4.84 4.72 7 48 5.05 4.83 11 84 (a) Process the results in the table to calculate both the masses of volatile liquid Y used and the volumes of vaporised Y. [2] (b) Plot a graph on the grid on page 9 to show the relationship between mass of liquid Y and volume of vapour Y. Use a cross (×) to plot each data point. Draw the line of best fit. [2]

9 9701/52/M/J/16 © UCLES 2016 [Turn over 90 80 70 60 50 40 30 volume of vapour Y / cm3 mass of liquid Y / g 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24

10 9701/52/M/J/16 © UCLES 2016 (c) Liquid Y evaporates easily, even at room temperature. This can cause anomalous results giving points below the line of best fit. (i) Explain how such anomalies occur. … … [1] (ii) With reference to the experimental procedure, explain how this source of error could be minimised. … … … [1] (d) (i) Determine the gradient of your graph. State the co-ordinates of both points you used for your calculation. Record the value of the gradient to three significant figures. co-ordinates 1 … co-ordinates 2 … gradient = … [2] (ii) Use the gradient value in (i) and the mathematical relationship on page 7 to calculate the experimentally determined relative molecular mass of Y. experimentally determined Mr of Y = … [2]

11 9701/52/M/J/16 © UCLES 2016 [Turn over (e) Compound Y is a hydrocarbon that contains 85.7% carbon by mass. The diagram shows the mass spectrum of compound Y. 100 80 60 40 20 0 0 10 20 30 40 50 m / e relative abundance / % 60 70 80 90 100 Use all the information given to determine the molecular formula of Y. molecular formula of Y … [2] [Total: 12]

12 9701/52/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 5 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/52 Paper 5 Planning, Analysis and Evaluation May/June 2016 MARK SCHEME Maximum Mark: 30 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 52 © Cambridge International Examinations 2016 Question Expected answer Mark 1 (a) (As the E o cell value increases) ∆Hr decreases or ∆Hr becomes more negative or ∆Hr becomes more exothermic. AND The more reactive the metal then the greater the energy release will be. OR Energy output of both reactions is dependent upon the difference in reactivity (of metals). [1] (b) Independent variable: The (type of) metal Dependent variable: temperature change or rise or increase OR enthalpy change [1] [1] (c) (i) Diagram should indicate a labelled insulated container AND a labelled thermometer in the liquid. [1] (ii) Mass of metal before and after Initial temperature (before metal added) AND Highest temperature (after metal added) [1] [1] (iii) Wear gloves [1] (iv) Moles CuSO4 = 0.025 mol, therefore moles of magnesium = 0.025 mol (minimum) mass Mg > (0.025 × 24.3 =) 0.6075 g AND mass required value is greater than 0.6075 g [1] [1] (v) Larger surface area AND causes increased rate of reaction [1] (vi) Ensure uniformity of heating (of solution) [1]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 52 © Cambridge International Examinations 2016 Question Expected answer Mark (d) 50.0 × 4.18 × 58.5 = 12 226.5 (J) ∆Hr = 12 226.5 / 0.025 = 489 000 = – 489 1000 [1] [1] (e) Complete circuit involving labelled voltmeter; labelled salt bridge; two separate solutions; (Solutions are) magnesium sulfate or MgSO4 with magnesium or Mg rod and copper(II) sulfate CuSO4 with copper or Cu rod Concentration of solution(s) is 1 mol dm–3 or 1 M [1] [1] [1] (f) So that values can be compared [1] (g) Both ∆Hr (Zn) and ∆Hr (Fe) values which are consistent with the prediction in (a). [1] [18]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 52 © Cambridge International Examinations 2016 Question Expected answer Mark 2 (a) Mass of liquid Y used / g Volume of vapour Y / cm3 0.15 48 0.10 35 0.21 72 0.17 58 0.24 83 0.09 31 0.20 70 0.23 79 0.12 41 0.22 73 All mass values. All volume values. [1] [1] (b) Candidate’s points plotted correctly from table in 2(a). Line of best fit drawn. [1] [1]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 52 © Cambridge International Examinations 2016 Question Expected answer Mark (c) (i) Y evaporates from the (hypodermic) syringe OR Y evaporates before injection OR Y evaporates before weighing / after injection [1] (ii) (Stop evaporation by) Keeping the syringe as cool as possible OR Closing off the needle end to stop evaporation OR Minimising length of time between each weighing [1] (d) (i) correct co-ordinates. correct calculation of the gradient must be three significant figures [1] [1] (ii) Calculation of Mr = 3.07×104 / gradient in 2(d)(i) Answer [1] [1] (e) Mr (from mass spectrum) = 84 OR empirical formula = CH2 OR ratio of C and H seen as 1:2 Y is C6H12 [1] [1] [12]