Cambridge A Level Chemistry 9701 — 2014 Oct/Nov Paper 5 · Variant 3

This document consists of 10 printed pages and 2 blank pages. [Turn over IB14 11_9701_53/3RP © UCLES 2014 *0255060262* 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. 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 9701/53 Paper 5 Planning, Analysis and Evaluation October/November 2014 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. Cambridge International Examinations Cambridge International Advanced Level

2 9701/53/O/N/14 © UCLES 2014 1 The enthalpy change, ∆Hr, for the reaction between magnesium atoms and aluminium ions to produce magnesium ions and aluminium atoms cannot be determined directly. However both metals react with dilute sulfuric acid and, using the enthalpy changes for these reactions, it is possible to use Hess’ Law to determine ∆Hr. You are to plan experiments that will enable you to determine the value of the enthalpy change for the reaction of 1 mol of magnesium with excess aqueous aluminium ions. You are provided with: ● 0.30 g of magnesium ribbon, ● 0.30 g of aluminium foil, ● 1.00 mol dm–3 sulfuric acid, ● standard laboratory equipment. (a) ● Write an equation for the reaction of magnesium and sulfuric acid. … ● Write an equation for the reaction of aluminium and sulfuric acid. … [2] (b) For the experiment to measure the enthalpy change when magnesium reacts with sulfuric acid name: (i) the independent variable, … [1] (ii) the dependent variable. … [1]

3 9701/53/O/N/14 © UCLES 2014 [Turn over (c) In the experiment, 20.0 cm3 of 1.00 mol dm–3 sulfuric acid is used with 0.30 g of magnesium. (i) Calculate the minimum volume in cm3 of sulfuric acid required to react completely with 0.30 g of magnesium. [Ar: Mg, 24.3] [1] (ii) Suggest why 20.0 cm3 of sulfuric acid is used. … … [1] (d) You are also provided with 0.30 g of aluminium. Calculate the minimum volume of 1.00 mol dm–3 sulfuric acid required to react completely with 0.30 g of aluminium. [Ar: Al, 27.0] [2]

4 9701/53/O/N/14 © UCLES 2014 (e) Explain how you would carry out the experiment using the 0.30 g magnesium. (i) List the measurements you would make. … … … … [1] (ii) How would you do the experiment to make sure the results obtained would be as accurate as possible? … … … … [1] (iii) How would you use the measurements made in the experiment to determine the enthalpy change of the reaction between 1 mol of magnesium and sulfuric acid? … … … … … … … … [2]

5 9701/53/O/N/14 © UCLES 2014 [Turn over (f) Write an ionic equation for the reaction between magnesium and aqueous aluminium ions. If the enthalpy change of the reaction between magnesium and sulfuric acid is ∆H1 and that for aluminium and sulfuric acid is ∆H2, use Hess’ Law to determine the enthalpy change, ∆Hr, for the reaction between magnesium and aqueous aluminium ions. Then determine the enthalpy change for 1 mol of magnesium in terms of ∆Hr. … … … … … … … … [3] [Total: 15]

6 9701/53/O/N/14 © UCLES 2014 2 An aqueous solution of nickel(II) sulfate, NiSO4, has a concentration of exactly 0.500 mol dm–3. In an experiment, 100.0 cm3 of this solution was accurately measured into a beaker and 0.0200 mol of solid potassium iodate(V), KIO3, was added to it. After stirring, a saturated solution of nickel(II) iodate was formed together with a precipitate of nickel(II) iodate. The precipitate was fi ltered off, dried and weighed. The mass of precipitate obtained was recorded in the table below. The experiment was repeated six more times using 100.0 cm3 of aqueous nickel(II) sulfate each time but adding increasing amounts of solid potassium iodate(V). The results obtained from these experiments were also recorded in the table below. experiment number amount of potassium iodate(V) added / mol mass of precipitate formed / g 1 0.0200 3.87 2 0.0300 6.71 3 0.0400 7.92 4 0.0500 8.80 5 0.0600 11.97 6 0.0700 13.95 7 0.0800 15.92 The concentration of ions in a saturated solution of a slightly soluble salt can be expressed using a solubility product. For nickel(II) iodate this is defi ned as: solubility product = [Ni2+(aq)][IO3 –(aq)]2 (a) (i) Write an ionic equation for the reaction that has taken place. Include state symbols. … [1] (ii) Use the equation in (i) to deduce the amount in mol of potassium iodate(V) that would react with the nickel(II) sulfate solution in this experiment. [1] (iii) If, after the amount in (ii) had been added further potassium iodate(V) was added, state what effect, if any, this would have on the mass of precipitate obtained. … … … [1]

7 9701/53/O/N/14 © UCLES 2014 [Turn over (b) (i) Plot points on the grid below to show the amount in mol of potassium iodate(V) added against the mass of precipitate formed. Draw a line of best fi t. 0.00 0.02 0.04 0.06 0.08 0.10 0.12 22.0 20.0 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 potassium iodate(V) added / mol mass of precipitate formed / g [2]

8 9701/53/O/N/14 © UCLES 2014 (ii) Circle any anomalous point(s) on your graph. [1] (iii) Suggest which part of the experimental procedure would make it diffi cult to achieve accurate results. … … … … [1] (iv) Add points on your graph to indicate the approximate mass of precipitate that would be obtained if each of the following amounts in mol of potassium iodate(V) were added. ● 0.1000 mol ● 0.1200 mol [2] (c) (i) In this reaction some of the nickel(II) iodate has been precipitated but some remains dissolved. Calculate the total mass of nickel(II) iodate (both precipitated and dissolved) formed in experiment 3 when all of the added potassium iodate(V) ions have fully reacted with nickel(II) sulfate. The relative formula mass of nickel(II) iodate is 408.7. [1]

9 9701/53/O/N/14 © UCLES 2014 [Turn over (ii) Use your answer to (i) and the mass of precipitate of nickel(II) iodate in experiment 3 to calculate the mass of nickel(II) iodate dissolved in solution. Calculate the amount in moles of nickel(II) iodate in solution. Calculate the amount in moles of iodate(V) ions that remain in the 100.0 cm3 of solution. [3]

10 9701/53/O/N/14 © UCLES 2014 (iii) The solubility product of nickel(II) iodate = [Ni2+(aq)][IO3 –(aq)]2. In experiment 3, the amount in moles of Ni2+(aq) that remain in the 100.0 cm3 of solution is 0.0306. Use this, and your fi nal answer in (ii), to calculate the solubility product. [2] [Total: 15]

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® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Level MARK SCHEME for the October/November 2014 series 9701 CHEMISTRY 9701/53 Paper 5 (Planning, Analysis and Evaluation), maximum raw mark 30 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 A Level – October/November 2014 9701 53 © Cambridge International Examinations 2014 Question Expected Answer Additional Guidance Mark 1 (a) (i) (ii) Mg + H2SO4
MgSO4 + H2 2Al + 3H2SO4
Al2(SO4)3 + 3H2 1 1 [2] (b) (i) (ii) The mass of magnesium The temperature change 1 1 [1] [1] (c) (i) (ii) 12.35 cm3 ECF equation in (a) The sulfuric acid must be in excess OR to ensure all the Mg has reacted / disappeared / dissolved / is the limiting reagent 1 1 [1] [1] (d) mol of Al = 0.011 (mol) AND mol of sulfuric acid = 0.0167 (mol) Volume of sulfuric acid =16.67 cm3 1 1 [2] (e) (i) The volume / mass of sulfuric acid / solution OR a stated volume of sulfuric acid. AND The initial / start temperature (of the acid) AND The final / end temperature (reached by the acid) 1 [1] (ii) Insulate (the reaction mixture) OR Stir (the mixture while the reaction is taking place) 1 [1]

Page 3 Mark Scheme Syllabus Paper Cambridge International A Level – October/November 2014 9701 53 © Cambridge International Examinations 2014 Question Expected Answer Additional Guidance Mark (iii) Calculate the heat produced in the reaction using (Q=) mc ∆T Convert to 1 mol 1 1 [2] (f) 3Mg + 2Al3+
3Mg2+ + 2Al (∆Hr = ) 3∆H1 – 1∆H2 Or a suitable Hess’ Law cycle ∆Hr 3Mg + 2Al3+ 3Mg2+ + 2Al 1∆H2 3∆H1 3Mg + 2Al ∆Hr/3 1 1 1 [3]

Page 4 Mark Scheme Syllabus Paper Cambridge International A Level – October/November 2014 9701 53 © Cambridge International Examinations 2014 Question Expected Answer Additional Guidance Mark 2 (a) (i) (ii) (iii) Ni2+(aq) +2IO3 –(aq)
Ni(IO3)2(s) 0.1000 More precipitate will form 1 1 1 [1] [1] [1] (b) (i) All points plotted correctly Straight line drawn through the origin up to at least exp 7. (If all points do not lie on the line then the net deviation of the non-anomalous points on each side of the best fit line must be approximately the same.) 1 1 [2] (ii) Points at 0.0300 mol and 0.0500 mol 1 [1] (iii) Loss of precipitate during transfer to filter OR Precipitate not dry OR Not weighing to constant mass OR Precipitate contains ionic materials not removed 1 [1] (iv) Point at 0.1000 lies on the extrapolated drawn line of best fit. Point at 0.1200 either at the same value as 0.1000 or slightly higher value 1 1 [2] (c) (i) 8.174 g 1 [1]

Page 5 Mark Scheme Syllabus Paper Cambridge International A Level – October/November 2014 9701 53 © Cambridge International Examinations 2014 Question Expected Answer Additional Guidance Mark (ii) 0.254 g (from c(i) – 7.92) 0.000621 (mol) IO3 – = 0.00124 (mol) 1 1 1 [3] (iii) [Ni2+] = 0.306 AND [IO3 –] = 0.0124 ECF 4.71 x 10–5 1 1 [2]