Cambridge A Level Chemistry 9701 — 2015 Oct/Nov Paper 3 · Variant 3

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 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. Qualitative Analysis Notes are printed on pages 10 and 11. A Periodic Table is printed on page 12. 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 9701/33 Paper 3 Advanced Practical Skills 1 October/November 2015 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confi dential Instructions Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level This document consists of 12 printed pages. [Turn over IB15 11_9701_33/2RP © UCLES 2015 *3461274007* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/33/O/N/15 © UCLES 2015 1 The formula of hydrated copper(II) sulfate is CuSO4.xH2O where x is the number of moles of water of crystallisation in one mole of salt. You will determine the value of x by titration. When aqueous copper(II) ions react with aqueous iodide ions, I–, iodine is produced. 2Cu2+(aq) + 4I–(aq) → I2(aq) + 2CuI(s) The amount of iodine, I2, produced can be found by titrating it with aqueous thiosulfate ions, S2O3 2–. 2S2O3 2–(aq) + I2(aq) → S4O6 2–(aq) + 2I–(aq) FA 1 is aqueous CuSO4.xH2O containing 26.2 g dm–3. FA 2 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. FA 3 is aqueous potassium iodide, KI. starch indicator (a) Method ● Pipette 25.0 cm3 of FA 1 into a conical flask. ● Use the measuring cylinder to add 15 cm3 of FA 3, an excess of KI, to the conical flask. The solution will turn brown because iodine is formed. ● Fill the burette with FA 2. ● Add FA 2 from the burette until the colour of the mixture changes to pale brown. ● Add 10 drops of starch indicator. The mixture will turn blue-black. ● Continue adding FA 2 from the burette until the dark colour suddenly disappears to leave an off-white solid. This is the end point of the titration. ● Carry out a rough titration and record your burette readings in the space below. The rough titre is … cm3. ● Carry out as many accurate titrations as you think necessary to obtain consistent results. ● Make certain any recorded results show the precision of your practical work. ● Record in a suitable form below, all your burette readings and the volume of FA 2 added in each accurate titration. [7] I II III IV V VI VII

3 9701/33/O/N/15 © UCLES 2015 [Turn over (b) From your accurate titration results, obtain a suitable value to be used in your calculations. Show clearly how you have obtained this value. 25.0 cm3 of FA 1 required … cm3 of FA 2. [1] (c) Calculations Show your working and appropriate signifi cant fi gures in each step of your calculations. (i) Calculate the number of moles of thiosulfate ions present in the volume of FA 2 you have calculated in (b). moles of S2O3 2– = … mol (ii) Use your answer to (i), and the equations for the reactions involved, to deduce the number of moles of Cu2+ present in 25.0 cm3 of FA 1. 2Cu2+(aq) + 4I–(aq) → I2(aq) + 2CuI(s) 2S2O3 2–(aq) + I2(aq) → S4O6 2– (aq) + 2I–(aq) moles of Cu2+ = … mol (iii) Use your answer to (ii) and the mass of CuSO4.xH2O present in the solution, to calculate the relative molecular mass, Mr, of CuSO4.xH2O. Mr of CuSO4.xH2O = … (iv) Determine the value of x. (Use data from the Periodic Table on page 12.) x = … [6] [Total: 14]

4 9701/33/O/N/15 © UCLES 2015 2 FA 4 is an impure sample of hydrated calcium chloride, CaCl 2.2H2O. On heating, hydrated calcium chloride loses its water of crystallisation. CaCl 2.2H2O(s) → CaCl 2(s) + 2H2O(g) You will determine the purity of FA 4 by measuring the loss in mass that occurs when it is heated. The impurity present in FA 4 is not decomposed on heating. (a) Method You should read the instructions carefully before starting any practical work and draw a table for your results in the space below. ● Weigh a crucible and record its mass. ● Add between 1.80 g and 2.00 g of FA 4 into the crucible. ● Reweigh the crucible and its contents and record the mass. ● Place the crucible on the pipe-clay triangle and heat gently for 1 minute and then strongly for a further 2 minutes. ● Allow the crucible and its contents to cool. Reweigh the crucible and contents and record the mass. ● Heat the crucible strongly for a further 2 minutes. Allow it to cool. Reweigh the crucible and contents and record the mass. ● Repeat the heating, cooling and weighing until you are satisfied that all the water of crystallisation has been removed. ● Calculate and record the mass of FA 4 used and the total mass of water lost. While you are waiting for the crucible to cool, you may wish to start work on Question 3. [6] I II III IV V VI

5 9701/33/O/N/15 © UCLES 2015 [Turn over (b) Calculations Show your working and appropriate signifi cant fi gures in the fi nal answer to each stage of your calculations. (i) The percentage loss in mass on heating is defi ned as the original mass the loss in mass on heating × 100. Calculate the percentage loss in mass of FA 4. percentage loss in mass = … % (ii) Calculate the percentage loss in mass when pure hydrated calcium chloride, CaCl 2.2H2O, is heated. percentage loss in mass = … % (iii) Use your results to (i) and (ii) to calculate the percentage purity of FA 4, impure CaCl 2.2H2O. percentage purity = … % [3] (c) A student carried out this experiment using 2.60 g of FA 4. Suggest whether this experiment would give a more accurate result for the percentage purity of FA 4. Explain your answer. … … [1]

6 9701/33/O/N/15 © UCLES 2015 (d) In your calculations you assumed that the impurity in FA 4 does not decompose on heating. State how the percentage purity that you calculated in (b)(iii) would change if the impurity were to decompose on heating. Explain your answer. … … [1] [Total: 11]

7 9701/33/O/N/15 © UCLES 2015 [Turn over 3 Qualitative Analysis At each stage of any test you are to record details of the following. ● colour changes seen ● the formation of any precipitate ● the solubility of such precipitates in an excess of the reagent added Where gases are released they should be identifi ed by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. No additional tests for ions present should be attempted. If any solution is warmed, a boiling tube MUST be used. Rinse and reuse test-tubes and boiling tubes where possible. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. (a) (i) FA 5, FA 6 and FA 7 are aqueous solutions each containing one anion and one cation. Carry out the experiments described below and record your observations for each solution in the table. FA 5 FA 6 FA 7 To a 1 cm depth in a test-tube, add a 1 cm depth of aqueous sodium carbonate. To a 1 cm depth in a test-tube, add a 1 cm depth of aqueous copper(II) sulfate. To a 1 cm depth in a test-tube, add a 1 cm depth of aqueous barium chloride or aqueous barium nitrate. (ii) What ion is present in both FA 6 and FA 7? … (iii) The anion in FA 5 is one of carbonate, chloride, nitrate or sulfate. Which anion is present in FA 5? … (iv) Write the ionic equation, including state symbols, for the reaction between FA 5 and aqueous copper(II) sulfate. … [7]

8 9701/33/O/N/15 © UCLES 2015 (b) FA 8 contains two anions and two cations from the lists on pages 10 and 11. • To a 5 cm depth of distilled water in a boiling tube, add all the FA 8. • Shake the boiling tube thoroughly for one minute to make sure that no more of the solid will dissolve. • Filter the mixture into a clean boiling tube. • Place the filter funnel in a conical flask and wash the residue with a little distilled water. • Keep both filtrate and residue for tests (i) and (ii) below. (i) Tests on the fi ltrate (the solution in the boiling tube) Carry out the following tests and record your observations in the table below. test observations To a 1 cm depth of the fi ltrate in a test-tube, add aqueous sodium hydroxide, then add aqueous hydrogen peroxide. (ii) Tests on the residue Carry out the following tests and record your observations in the table below. test observations Place the funnel containing the residue into a clean boiling tube. Pour approximately 5 cm3 of dilute nitric acid onto the residue. Collect a 1 cm depth of solution in the boiling tube. Remove the funnel and return it to the conical fl ask. To this solution in the boiling tube, add aqueous sodium hydroxide.

9 9701/33/O/N/15 © UCLES 2015 [Turn over (iii) Identify two cations present in FA 8. cations present … and … (iv) Identify one anion present in FA 8. anion present … (v) Suggest what type of reaction is happening when hydrogen peroxide is added in test (b)(i). … [8] [Total: 15]

10 9701/33/O/N/15 © UCLES 2015 Qualitative Analysis Notes Key: [ppt. = precipitate] 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) no ppt. (if 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 giving dark green solution 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

11 9701/33/O/N/15 © UCLES 2015 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; NO liberated by dilute acids (colourless NO → (pale) brown NO2 in air) sulfate, SO4 2–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids) sulfi te, SO3 2–(aq) SO2 liberated with dilute acids; 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 sulfur dioxide, SO2 turns acidifi ed aqueous potassium manganate(VII) from purple to colourless

12 9701/33/O/N/15 © UCLES 2015 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 140 Ce Cerium 58 141 Pr Praseodymium 59 144 Nd Neodymium 60 Pm Promethium 61 150 Sm Samarium 62 152 Eu Europium 63 157 Gd Gadolinium 64 159 Tb Terbium 65 163 Dy Dysprosium 66 165 Ho Holmium 67 167 Er Erbium 68 169 Tm Thulium 69 173 Yb Ytterbium 70 175 Lu Lutetium 71 Th Thorium 90 Pa Protactinium 91 U Uranium 92 Np Neptunium 93 Pu Plutonium 94 Am Americium 95 Cm Curium 96 Bk Berkelium 97 Cf Californium 98 Es Einsteinium 99 Fm Fermium 100 Md Mendelevium 101 No Nobelium 102 Lr Lawrencium 103 1.0 H Hydrogen 1 6.9 Li Lithium 3 23.0 Na Sodium 11 24.3 Mg Magnesium 12 40.1 Ca Calcium 20 45.0 Sc Scandium 21 47.9 Ti Titanium 22 50.9 V Vanadium 23 52.0 Cr Chromium 24 54.9 Mn Manganese 25 55.8 Fe Iron 26 58.9 Co Cobalt 27 58.7 Ni Nickel 28 63.5 Cu Copper 29 65.4 Zn Zinc 30 69.7 Ga Gallium 31 27.0 Al Aluminium 13 10.8 B Boron 5 12.0 C Carbon 6 14.0 N Nitrogen 7 16.0 O Oxygen 8 19.0 F Fluorine 9 28.1 Si Silicon 14 31.0 P Phosphorus 15 32.1 S Sulfur 16 35.5 Cl Chlorine 17 39.9 Ar Argon 18 20.2 Ne Neon 10 4.0 He Helium 2 72.6 Ge Germanium 32 74.9 As Arsenic 33 79.0 Se Selenium 34 79.9 Br Bromine 35 83.8 Kr Krypton 36 39.1 K Potassium 19 87.6 Sr Strontium 38 88.9 Y Yttrium 39 91.2 Zr Zirconium 40 92.9 Nb Niobium 41 95.9 Mo Molybdenum 42 Tc Technetium 43 101 Ru Ruthenium 44 103 Rh Rhodium 45 106 Pd Palladium 46 108 Ag Silver 47 112 Cd Cadmium 48 115 In Indium 49 119 Sn Tin 50 122 Sb Antimony 51 128 Te Tellurium 52 127 I Iodine 53 131 Xe Xenon 54 137 Ba Barium 56 139 La Lanthanum 57 * 178 Hf Hafnium 72 181 Ta Tantalum 73 184 W Tungsten 74 186 Re Rhenium 75 190 Os Osmium 76 192 Ir Iridium 77 195 Pt Platinum 78 197 Au Gold 79 201 Hg Mercury 80 204 Tl Thallium 81 207 Pb Lead 82 209 Bi Bismuth 83 Po Polonium 84 At Astatine 85 Rn Radon 86 Rf Rutherfordium 104 Db Dubnium 105 Sg Seaborgium 106 Bh Bohrium 107 Hs Hassium 108 Mt Meitnerium 109 Uun Ununnilium 110 Uuu Unununium 111 Uub Ununbium 112 Uuq Ununquadium 114 Uuh Ununhexium 116 Uuo Ununoctium 118 Fr Francium 87 Ac Actinium 89 9.0 Be Beryllium 4 I II III IV V VI VII 0 85.5 Rb Rubidium 37 133 Cs Caesium 55 Ra Radium 88 a X b a = relative atomic mass X = atomic symbol b = proton (atomic) number Key *58-71 Lanthanides 90-103 Actinides The Periodic Table of the Elements *

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the October/November 2015 series 9701 CHEMISTRY 9701/33 Paper 3 (Advanced Practical Skills 1), maximum raw mark 40 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 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 – October/November 2015 9701 33 © Cambridge International Examinations 2015 Question Indicative material Mark Total 1 (a) I Initial and final readings and titre recorded for rough titre and accurate titre details tabulated (minimum 2 × 2 ‘boxes’) 1 II Headings and units correct for accurate titrations Headings: initial / final (burette) reading / volume or reading / volume at start / finish and titre or volume / FA 2 and added / used / titrated [not ‘difference’ or ‘total’] and Units: (cm3) or / cm3 or in cm3 [or cm3 by every entry] 1 III All accurate burette readings are recorded to the nearest 0.05 cm3 Do not award this mark if: 50(.00) is used as an initial burette reading; more than one final burette reading is 50(.00); any burette reading is greater than 50(.00) there is only one accurate titration 1 IV Has two uncorrected, accurate titres within 0.1 cm3 Do not award this mark if having performed two titres within 0.1 cm3 a further titration is performed which is more than 0.10 cm3 from the closer of the initial two titres, unless any further titrations, within 0.1 cm3 of any other titration have also been carried out. Do not award the mark if any ‘accurate’ burette readings (apart from initial 0) are given to zero dp. 1 Examiner rounds any burette readings to the nearest 0.05 cm3, checks subtractions and then selects the ‘best titres’ using the hierarchy: • two (or more) accurate identical titres then • two (or more) accurate titres within 0.05 cm3, then two (or more) accurate titres within 0.10 cm3, etc. These best titres should be used to calculate the mean corrected titre to the nearest 0.01 cm3. Examiner calculates the difference (δ) between the mean titres obtained by the candidate and the Supervisor. Accuracy marks awarded as shown. Award V, VI and VII if δ ⩽ 0.30 cm3 Award V and VI if 0.30 < δ ⩽ 0.50 cm3 Award V if 0.50 < δ ⩽ 0.80 cm3. Spread penalty: if the two best titres used by the Examiner were ⩾ 0.5 cm3 apart, cancel one accuracy mark. 1 1 1 [7]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9701 33 © Cambridge International Examinations 2015 Question Indicative material Mark Total (b) Candidate must average two (or more) accurate titres where the total spread is ⩽ 0.20 cm3. Working must be shown or ticks must be put next to the two (or more) accurate readings selected. The mean should normally be quoted to 2 decimal places rounded to the nearest 0.01. Two special cases where the mean may not be to 2 dp: allow mean to 3 dp only for 0.025 or 0.075, e.g. 26.325; allow mean to 1 dp if all accurate burette readings were given to 1 dp and the mean is exactly correct. e.g. 26.0 and 26.2 = 26.1 is correct but 26.0 and 26.1 = 26.1 is incorrect. Note: the candidate’s mean will sometimes be marked as correct even if it is different from the mean calculated by the Examiner for the purpose of assessing accuracy. 1 [1] (c) (i) Correctly calculates moles = (b) × 0.1 / 1000 and answer to 3 or 4 significant figures 1 (ii) Same as (c)(i) 1 (iii) Shows correct use of either factor of 40 (1000 / 25) or mole ratio Answer consistent with data shown to 3 or 4 sf Mr = 26.2 /( (c)(ii) × 40) 1 1 (iv) x = (Mr – 159.6) / 18 1 Answer to nearest positive integer with use of either 159.6 or 18 and some use of experimental data. 1 [6] Qn 1 Total [14]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9701 33 © Cambridge International Examinations 2015 Question Indicative material Mark Total 2 (a) I Mass of FA 4 used by candidate was between 1.80 g and 2.00 g 1 II Suitable table, with unambiguous headings and correct units, in parallel columns or rows and a minimum of four balance readings entered • mass crucible / g (not weight) • mass crucible + FA 4 (g) • mass crucible + contents / FA 4 after heating in g • mass crucible + contents / FA 4 after 2nd / further heating / g 1 III All balance readings (minimum 3) recorded to same dp and mass of FA 4 used and water lost correctly calculated 1 IV Heating repeated until constant mass (final readings within 0.05 g for 2 dp balance and identical for 1 dp balance) 1 V and VI Examiner calculates and writes % next to table Calculate 4 FA mass 100 lost water mass total × to 1 dp Award V if % loss in range 12.8 to 16.8 Award VI if % loss in range 13.8 to 15.8 1 1 [6] (b) (i) Correctly calculated loss in mass / mass FA 4 to 2 – 4 sf 1 (ii) Correctly calculates % loss = 36 × 100 / 147.1 1 (iii) % purity = (ii) 100 (i)× 1 [3] (c) (Yes) because a greater mass used and so percentage error in weighing less. or (No) because there is more water to be lost so more spitting and frothing so percentage error in mass lost will be greater 1 [1] (d) Greater loss of mass therefore apparent % purity is high(er) / the value / it would increase 1 [1] Qn 2 Total [11]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9701 33 © Cambridge International Examinations 2015 Question Indicative material Mark Total FA 5 is Na2CO3(aq); FA 6 is H2SO4(aq); FA 7 is CH3COOH(aq); FA 8 is MnSO4(s) and MgCO3(s) 3 (a) (i) See table FA 5 FA 6 FA 7 + Na2CO3 no reaction effervescence / bubbling / fizzing or gas turns limewater milky / cloudy white / white ppt effervescence / bubbling / fizzing or gas turns limewater milky / cloudy white / white ppt + CuSO4 blue ppt (not dark blue) no reaction / no change / no ppt / pale or light blue (solution) (not ‘–‘ or ‘no observation’) no reaction / no change / no ppt / pale or light blue (solution) (not ‘–‘ or ‘no observation’) + BaCl2 / Ba(NO3)2 white ppt white ppt no reaction / no change / no ppt 4 (ii) H+ / hydrogen ion 1 (iii) CO3 2− / carbonate 1 (iv) Cu2+(aq) + CO3 2−(aq) → CuCO3(s) 1 [7]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9701 33 © Cambridge International Examinations 2015 (b) (i) + NaOH: off white / buff / beige / pale or light brown (not cream) ppt and either darkens on standing or insoluble in excess 1 + H2O2: (turns) brown / darker brown / brown-black (not black) 1 fizzing / effervescence / bubbling or gas relights glowing splint 1 (ii) + HNO3: fizzing / effervescence / bubbling or limewater turns milky / cloudy white / white ppt 1 + NaOH: White ppt and insoluble in excess 1 (iii) Mn2+ / manganese(II) and Mg2+ / magnesium 1 (iv) CO3 2− / carbonate 1 (v) Redox / decomposition of H2O2 / disproportionation allow oxidation of Mn2+ / oxidation or reduction of H2O2 1 [8] Qn 3 Total [15]