Cambridge A Level Chemistry 9701 — 2018 Oct/Nov Paper 3 · Variant 6

READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Give details of the practical session and laboratory where appropriate, in the boxes provided. 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. Qualitative Analysis Notes are printed on pages 14 and 15. A copy of the Periodic Table is printed on page 16. 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 9701/36 Paper 3 Advanced Practical Skills 2 October/November 2018  2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level This document consists of 14 printed pages and 2 blank pages. [Turn over IB18 11_9701_36/6RP © UCLES 2018 *5884351244* Session Laboratory For Examiner’s Use 1 2 Total

2 9701/36/O/N/18 © UCLES 2018 Quantitative Analysis Read through the whole method before starting any practical work. Where appropriate, prepare a table for your results in the space provided. Show your working and appropriate significant figures in the final answer to each step of your calculations. 1 Iron(III) ions oxidise iodide ions, I–, to iodine, I2. 2Fe3+(aq) + 2I–(aq) 2Fe2+(aq) + I2(aq) In this experiment you will investigate how the rate of this reaction is affected by the concentration of Fe3+ ions. To do this you will add thiosulfate ions, S2O3 2–, and starch indicator to a mixture of Fe3+(aq) and I–(aq). The iodine produced by the reaction reacts immediately with the thiosulfate ions and is reduced back to iodide. I2(aq) + 2S2O3 2–(aq) 2I–(aq) + S4O6 2–(aq) When all the thiosulfate has reacted, the iodine remaining in solution turns the starch indicator blue‑black. The rate of reaction can be determined by timing how long it takes for the reaction mixture to turn blue-black. FB 1 is 0.0500 mol dm–3 acidified iron(III) chloride, FeCl 3. FB 2 is 0.0500 mol dm–3 potassium iodide, KI. FB 3 is 0.00500 mol dm–3 sodium thiosulfate, Na2S2O3. FB 4 is starch indicator.

3 9701/36/O/N/18 © UCLES 2018 [Turn over (a) Method Experiment 1 ● ● Fill the burette labelled FB 1 with FB 1. ● ● Run 20.00 cm3 of FB 1 into a 100 cm3 beaker. ● ● Using the measuring cylinder add the following to the second 100 cm3 beaker: ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of FB 4 ● ● Add the contents of the first beaker to the second beaker and start timing immediately. ● ● Stir the mixture once and place the beaker on a white tile. ● ● Stop timing as soon as the solution turns blue-black. Ignore any colour changes that occur before the intense blue-black colouration. ● ● Record this reaction time to the nearest second in the space provided on page 4. ● ● Rinse both beakers and shake dry. Rinse and dry the glass rod. Experiment 2 ● ● Fill a second burette with distilled water. ● ● Run 10.00 cm3 of FB 1 into a 100 cm3 beaker. ● ● Run 10.00 cm3 of distilled water into the same beaker containing FB 1. ● ● Using the measuring cylinder add the following to the second 100 cm3 beaker: ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of FB 4 ● ● Add the contents of the first beaker to the second beaker and start timing immediately. ● ● Stir the mixture once and place the beaker on a white tile. ● ● Stop timing as soon as the solution turns blue-black. Ignore any colour changes that occur before the intense blue-black colouration. ● ● Record this reaction time to the nearest second in the space provided on page 4. ● ● Rinse both beakers and shake dry. Rinse and dry the glass rod.

4 9701/36/O/N/18 © UCLES 2018 Experiments 3–5 ● ● Carry out three further experiments to investigate how the reaction time changes with different volumes of FB 1. Remember that the combined volume of FB 1 and distilled water must always be 20.00 cm3. Do not carry out an experiment using 15.00 cm3 of FB 1. Do not use a volume of FB 1 that is less than 5.00 cm3. Keep all FB labelled solutions for use in (e) and in Question 2. Record all your results in a single table. You should include the volume of FB 1, the volume of distilled water and the reaction time. The relative rate for the reaction is given by the following expression. relative rate = 1000 reaction time in seconds Use this expression to calculate the relative rate for each of your experiments and record the values in your results table.  [10] (b) On the grid opposite, plot the relative rate against the volume of FB 1. Include the origin in your plot. Label any points you consider anomalous. Draw a line of best fit. I II III IV V VI VII VIII IX X

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6 9701/36/O/N/18 © UCLES 2018 (c) From your graph, what conclusion can you make about the relationship between the relative rate for the reaction and the volume of FB 1 used? Explain your answer. … … … [2] (d) A student carried out the same experiment but used 15.00 cm3 of FB 1. The student recorded a value for the reaction time of 28 s. (i) Use your graph to calculate the time you would have expected to record if you had carried out an experiment using 15.00 cm3 of FB 1. Show the construction lines on your graph and show your working in the calculation.  reaction time = … s [2] (ii) Calculate the percentage difference between your value and that of the student. Show your working.  percentage difference = … % [1] (e) You are to carry out a sixth experiment. The concentrations of iron(III) chloride, sodium thiosulfate and starch indicator should all be the same as in Experiment 2 but the concentration of iodide ions should be twice the value that it is in Experiment 2. State the volume of each solution used and record the reaction time to the nearest second.  [2]

7 9701/36/O/N/18 © UCLES 2018 [Turn over (f) (i) 20.00 cm3 of 0.0500 mol dm–3 FeCl 3, FB 1, were reacted with excess KI, FB 2. Using the information on page 2, calculate the number of moles of I2 produced.  moles I2 = … mol [2] (ii) The iodine produced in (i) required 35.00 cm3 of a different solution of sodium thiosulfate for complete reaction. Calculate the concentration of the solution of sodium thiosulfate used.  concentration of Na2S2O3 = … mol dm–3 [1]  [Total: 24]

8 9701/36/O/N/18 © UCLES 2018 Qualitative Analysis Where reagents are selected for use in a test, the full name or correct formula of the element or compound must be given. At each stage of any test you are to record details of the following: ● colour changes seen; ● the formation of any precipitate and its solubility in an excess of the reagent added; ● the formation of any gas and its identification by a suitable test. You should indicate clearly at what stage in a test a change occurs. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests for ions present should be attempted. 2 (a) FB 1 is aqueous acidified iron(III) chloride, FeCl 3. FB 5 is 0.150 mol dm–3 sodium thiosulfate, Na2S2O3. (i) Carry out the following tests and record your observations. test observations To a 1 cm depth of FB 1 in a test-tube add a 1 cm depth of FB 5. Leave to stand until there is no further change, then add aqueous sodium hydroxide. To a 1 cm depth of FB 5 in a test‑tube add a few drops of dilute hydrochloric acid. Leave to stand. Rinse the tube thoroughly.  [3]

9 9701/36/O/N/18 © UCLES 2018 [Turn over (ii) In (i) you should have observed a reaction between Fe3+(aq) and S2O3 2–(aq). Do you think that this reaction affected your results in Question 1? Refer to the equations on page 2. Explain your answer. … … [1] (b) FB 6 is a solution containing a halide ion. (i) Carry out the following tests and record your observations. test observations To a 1 cm depth of FB 6 in a test-tube add aqueous silver nitrate, then add aqueous ammonia. To a 1 cm depth of FB 6 in a test-tube add aqueous silver nitrate, then add FB 5.  [2] (ii) The halide in FB 6 is … . [1]

10 9701/36/O/N/18 © UCLES 2018 (c) FB 7 is a solution of copper(II) sulfate, CuSO4. (i) Carry out the following tests and record your observations. test observations To a 1 cm depth of FB 7 in a test-tube add a 1 cm depth of FB 2, KI, then add FB 4, starch indicator. To a 1 cm depth of FB 7 in a test‑tube add a 1 cm depth of FB 5, then add a 1 cm depth of FB 2 followed by FB 4, starch indicator.  [3] (ii) Give the formula of one of the products formed in the reaction of FB 7 with FB 2 in the first test. … [1]

11 9701/36/O/N/18 © UCLES 2018 [Turn over (d) FB 8 is a solution of a salt containing one cation and one anion from those listed in the Qualitative Analysis Notes. The cation in FB 8 is one of Mg2+, Zn2+ or Al 3+. The anion in FB 8 is either SO3 2– or SO4 2–. (i) Select reagents and carry out tests to identify which ions are present in FB 8. Give details of your tests and observations.  [4] (ii) The formula of FB 8 is … . [1]  [Total: 16]

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14 9701/36/O/N/18 © UCLES 2018 Qualitative Analysis Notes 1 Reactions of aqueous cations ion reaction with NaOH(aq) NH3(aq) aluminium, Al 3+(aq) white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH4 +(aq) no ppt. ammonia produced on heating – barium, Ba2+(aq) faint white ppt. is nearly always observed unless reagents are pure no ppt. calcium, Ca2+(aq) white ppt. with high [Ca2+(aq)] no ppt. chromium(III), Cr3+(aq) grey-green ppt. soluble in excess grey-green ppt. insoluble in excess copper(II), Cu2+(aq) pale blue ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution iron(II), Fe2+(aq) green ppt. turning brown on contact with air insoluble in excess green ppt. turning brown on contact with air insoluble in excess iron(III), Fe3+(aq) red-brown ppt. insoluble in excess red-brown ppt. insoluble in excess magnesium, Mg2+(aq) white ppt. insoluble in excess white ppt. insoluble in excess manganese(II), Mn2+(aq) off-white ppt. rapidly turning brown on contact with air insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess zinc, Zn2+(aq) white ppt. soluble in excess white ppt. soluble in excess

15 9701/36/O/N/18 © UCLES 2018 2 Reactions of anions ion reaction carbonate, CO3 2– CO2 liberated by dilute acids chloride, Cl –(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)) bromide, Br –(aq) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)) iodide, I –(aq) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)) nitrate, NO3 –(aq) NH3 liberated on heating with OH–(aq) and Al foil nitrite, NO2 –(aq) NH3 liberated on heating with OH–(aq) and Al foil sulfate, SO4 2–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids) sulfite, SO3 2–(aq) gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids) 3 Tests for gases gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 gives a white ppt. with limewater (ppt. dissolves with excess CO2) chlorine, Cl 2 bleaches damp litmus paper hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint

16 9701/36/O/N/18 © UCLES 2018 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. Group The Periodic Table of Elements 1 H hydrogen 1.0 2 He helium 4.0 1 2 13 14 15 16 17 18 3 4 5 6 7 8 9 10 11 12 3 Li lithium 6.9 4 Be beryllium 9.0 atomic number atomic symbol Key name relative atomic mass 11 Na sodium 23.0 12 Mg magnesium 24.3 19 K potassium 39.1 20 Ca calcium 40.1 37 Rb rubidium 85.5 38 Sr strontium 87.6 55 Cs caesium 132.9 56 Ba barium 137.3 87 Fr francium – 88 Ra radium – 5 B boron 10.8 13 Al aluminium 27.0 31 Ga gallium 69.7 49 In indium 114.8 81 Tl thallium 204.4 6 C carbon 12.0 14 Si silicon 28.1 32 Ge germanium 72.6 50 Sn tin 118.7 82 Pb lead 207.2 22 Ti titanium 47.9 40 Zr zirconium 91.2 72 Hf hafnium 178.5 104 Rf rutherfordium – 23 V vanadium 50.9 41 Nb niobium 92.9 73 Ta tantalum 180.9 105 Db dubnium – 24 Cr chromium 52.0 42 Mo molybdenum 95.9 74 W tungsten 183.8 106 Sg seaborgium – 25 Mn manganese 54.9 43 Tc technetium – 75 Re rhenium 186.2 107 Bh bohrium – 26 Fe iron 55.8 44 Ru ruthenium 101.1 76 Os osmium 190.2 108 Hs hassium – 27 Co cobalt 58.9 45 Rh rhodium 102.9 77 Ir iridium 192.2 109 Mt meitnerium – 28 Ni nickel 58.7 46 Pd palladium 106.4 78 Pt platinum 195.1 110 Ds darmstadtium – 29 Cu copper 63.5 47 Ag silver 107.9 79 Au gold 197.0 111 Rg roentgenium – 30 Zn zinc 65.4 48 Cd cadmium 112.4 80 Hg mercury 200.6 112 Cn copernicium – 114 Fl flerovium – 116 Lv livermorium – 7 N nitrogen 14.0 15 P phosphorus 31.0 33 As arsenic 74.9 51 Sb antimony 121.8 83 Bi bismuth 209.0 8 O oxygen 16.0 16 S sulfur 32.1 34 Se selenium 79.0 52 Te tellurium 127.6 84 Po polonium – 9 F fluorine 19.0 17 Cl chlorine 35.5 35 Br bromine 79.9 53 I iodine 126.9 85 At astatine – 10 Ne neon 20.2 18 Ar argon 39.9 36 Kr krypton 83.8 54 Xe xenon 131.3 86 Rn radon – 21 Sc scandium 45.0 39 Y yttrium 88.9 57–71 lanthanoids 89–103 actinoids 57 La lanthanum 138.9 89 Ac lanthanoids actinoids actinium – 58 Ce cerium 140.1 90 Th thorium 232.0 59 Pr praseodymium 140.9 91 Pa protactinium 231.0 60 Nd neodymium 144.4 92 U uranium 238.0 61 Pm promethium – 93 Np neptunium – 62 Sm samarium 150.4 94 Pu plutonium – 63 Eu europium 152.0 95 Am americium – 64 Gd gadolinium 157.3 96 Cm curium – 65 Tb terbium 158.9 97 Bk berkelium – 66 Dy dysprosium 162.5 98 Cf californium – 67 Ho holmium 164.9 99 Es einsteinium – 68 Er erbium 167.3 100 Fm fermium – 69 Tm thulium 168.9 101 Md mendelevium – 70 Yb ytterbium 173.1 102 No nobelium – 71 Lu lutetium 175.0 103 Lr lawrencium –

This document consists of 8 printed pages. © UCLES 2018 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/36 Paper 3 Advanced Practical Skills 2 October/November 2018 MARK SCHEME Maximum Mark: 40 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 International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the October/November 2018 series for most Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 2 of 8 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with: • the specific content of the mark scheme or the generic level descriptors for the question • the specific skills defined in the mark scheme or in the generic level descriptors for the question • the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively: • marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate • marks are awarded when candidates clearly demonstrate what they know and can do • marks are not deducted for errors • marks are not deducted for omissions • answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors.

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 3 of 8 GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind.

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 4 of 8 Rounding errors and transcription errors are penalised only once in the paper. Question Answer Marks 1(a) I Constructs a table for results for 5 experiments and 4 columns. 1 II Appropriate headings and units for all recorded data given. Volumes in cm3 or / cm3 or (cm3). Time in seconds or / s or (s). Units for rate given as s–1 1 III All times recorded to the nearest second and volumes of FB 1 and water to at least 1 decimal place. 1 IV Three additional volumes chosen with intervals not less than 2.00 cm3 AND No experiment with FB 1 = 15.00 cm3 AND all volumes of FB 1 ≥ 5.00 cm3 AND at least one experiment between 5 cm3 and 10 cm3 1 V In all additional experiments water is added to make the same total volume. 1 VI All rates correctly calculated using 1000 / time AND 1 or 2 decimal place 1 VII + VIII Compare time for 20.00 cm3 of FB 1 with that of supervisor. Award VII for within 20% of supervisor rounded to nearest s. Award VII + VIII for within 10% of supervisor rounded to nearest s. 2 Examiner calculates supervisor’s ratio time expt 2 / time expt 1 to 2 dp. Calculate candidate t2 / t1 to 2 dp IX + X Compare ratio of time for 10.00 cm3 FB 1 / time for 20.00 cm3 FB 1 with that of supervisor. Award IX for within 0.20. Award IX + X for within 0.10. 2

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 5 of 8 Question Answer Marks 1(b) I Rate on y-axis and volume on x-axis. Axes clearly labelled (labels or units). 1 II Linear scales including origin; scale chosen so that plotted points and the origin use more than half of each axis 1 III All recorded points plotted correctly to within half a small square and in the correct square. Points that should be plotted on lines must be on lines, points that should not be on lines must not be on lines. Do not award for crosses or blobs more than half a small square thick. 1 IV Draws a line of best fit. This may be a straight line or smooth curve. Points must be balanced and line cannot be improved by rotation. 1 1(c) Straight line: Rate is proportional to volume of FB 1 OR Curved line: Rate is proportional to volume of FB 1 1 Rate is directly proportional to volume of FB 1 because straight line goes through origin / OR Rate is proportional to volume of FB 1 as straight line but not through origin. OR for curved line: It is not directly proportional because not a straight line 1 1(d)(i) Reads rate from graph to the nearest small square using vertical and horizontal construction lines and some evidence of its use in the calculation. 1 Correctly calculates time from candidate’s value for y-axis intercept to 2–4 sf 1 1(d)(ii) Correctly uses % difference to 2–4 significant figures 1

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 6 of 8 Question Answer Marks 1(e) Uses 20 cm3 of FB 2 and records time less than Experiment 2 (with 10 cm3 FB 1). 1 Volumes: FB 1 = 10 cm3 FB 2 = 20 cm3 FB 3 = 20 cm3 FB 4 = 10 cm3 1 1(f)(i) Moles Fe3+ = 0.001(0) or 0.05 × 20/1000 Moles I2 = 0.0005(0) 1 1 1(f)(ii) moles I2 in (i) × 2/0.035 Concentration for correct n(I2) = 0.029 / 0.0286 / 0.02857 mol dm–3 and answer to 2–4 sf 1 Question Answer Marks (FB 1 = Fe3+; FB 5 = S2O3 2–;) FB 6 = KBr(aq); FB 7 = CuSO4(aq); FB 8 = Al2(SO4)3 2(a)(i) (turns) purple and turns colourless (solution) / white or (pale) yellow ppt (on standing) 1 green / black / brown ppt on adding NaOH 1 white ppt 1 2(a)(ii) One of: Yes, as the Fe3+ does not all react with I– Yes, as all the S2O3 2‒ does not react with I2 Yes, as less S2O3 2‒ (present) to react with I2 No, as concentration of S2O3 2‒ is much lower in Q1 than in Q2 1

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 7 of 8 Question Answer Marks 2(b)(i) test observation + Ag+(aq) cream ppt ● + NH3(aq) ppt insoluble / partially soluble / no reaction / no (visible) change ● + Ag+(aq) cream ppt ● + FB 5 ppt soluble / (colourless) solution formed ● Two ● = 1 mark 2 2(b)(ii) Halide in FB 6 is Br‒ / bromide 1 2(c)(i) (solution) turns brown OR white / off-white / brown ppt not yellow ppt nor yellow solution AND black / blue-black / dark blue on addition of starch 1 Final colour and either initial colour or solution must be given. Solution turns from blue to pale yellow 1 no (colour) change / no reaction (on addition of FB 2 or of starch) 1 2(c)(ii) I2 OR CuI 1

9701/36 Cambridge International AS/A Level – Mark Scheme PUBLISHED October/November 2018 © UCLES 2018 Page 8 of 8 Question Answer Marks 2(d)(i) NaOH and NH3 1 BaCl2 / Ba(NO3)2 AND HCl / HNO3 OR acidified (aqueous) KMnO4 OR named mineral acid AND test any gas with KMnO4 1 With NaOH white ppt and sol in excess AND with NH3 white ppt and insol in excess 1 With BaCl2 / Ba(NO3)2 white ppt AND insoluble in acid OR (with KMnO4) no change / no reaction AND solution remains purple OR dichromate – no change AND solution remains orange OR (with named acid) no gas evolved / no change / no reaction AND KMnO4 (paper) stays purple 1 2(d)(ii) FB 8 is Al2(SO4)3 1