Cambridge A Level Chemistry 9701 — 2016 May/June Paper 3 · Variant 2

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 10 and 11. A copy of the 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 9701/32 Paper 3 Advanced Practical Skills 2 May/June 2016 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 12 printed pages. [Turn over IB16 06_9701_32/4RP © UCLES 2016 *6272270242* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/32/M/J/16 © UCLES 2016 1 In Questions 1 and 2 you will determine the relative atomic mass, Ar, of magnesium by two different methods. In the first method you will collect and measure the volume of gas given off in the reaction between a known mass of magnesium and a known amount of dilute sulfuric acid. The acid will be in excess. Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g) FB 1 is a strip of magnesium ribbon, Mg. FB 2 is 1.00 mol dm–3 sulfuric acid, H2SO4. (a) Method Read through the whole method before starting any practical work. The diagrams below may help you in setting up your apparatus. clamp water OR clamp water X X • Fill the tub with water to a depth of about 5 cm. • Fill the 250 cm3 measuring cylinder completely with water. Hold a piece of paper towel firmly over the top, invert the measuring cylinder and place it in the water in the tub. • Remove the paper towel and clamp the inverted measuring cylinder so the open end is in the water just above the base of the tub. • Pipette 25.0 cm3 of FB 2 into the reaction flask labelled X. • Check that the bung fits tightly in the neck of flask X, clamp flask X, and place the end of the delivery tube into the inverted 250 cm3 measuring cylinder. • Weigh the magnesium ribbon, FB 1, and record the mass in the space below. • Remove the bung from the neck of the flask. Add the magnesium ribbon, FB 1, into the acid in the flask and replace the bung immediately. Remove the flask from the clamp and swirl it to mix the contents. Swirl the flask occasionally until no more gas is evolved. Replace the flask in the clamp. • When no more gas is collected, measure and record the final volume of gas in the measuring cylinder in the space below. Keep the contents of the conical flask X for use in Question 2. Results [2]

3 9701/32/M/J/16 © UCLES 2016 [Turn over (b) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of gas collected in the measuring cylinder. [Assume that 1 mole of gas occupies 24.0 dm3 under these conditions.] moles of gas = … mol (ii) Use your answer to (i) and the mass of magnesium, FB 1, recorded in (a) to calculate the relative atomic mass, Ar, of magnesium. Ar of magnesium = … [3] [Total: 5]

4 9701/32/M/J/16 © UCLES 2016 2 You will determine the amount of sulfuric acid remaining in flask X after the reaction with magnesium in Question 1. You will do this by titration with sodium hydroxide of known concentration. 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l) FB 3 is 0.150 mol dm–3 sodium hydroxide, NaOH. bromophenol blue indicator (a) Method • Transfer all the contents of flask X from Question 1 into the 250 cm3 volumetric flask. • Rinse flask X with distilled water and add the washings to the volumetric flask. Add distilled water up to the mark. Stopper the volumetric flask and mix the contents thoroughly. • Label this solution FB 4. • Rinse the pipette and use it to transfer 25.0 cm3 of FB 4 into the conical flask. • Add about 10 drops of bromophenol blue to the conical flask. • Fill the burette with FB 3. • Perform a rough titration and record your burette readings in the space below. The end point is reached when the solution becomes a permanent blue-violet colour. The rough titre is … cm3. • Carry out as many accurate titrations as you think necessary to obtain consistent results. • Record, in a suitable form below, all of your burette readings and the volume of FB 3 added in each accurate titration. • Make certain any recorded results show the precision of your practical work. [7] (b) From your accurate titration results, obtain a suitable value for the volume of FB 3 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FB 4 required … cm3 of FB 3. [1] I II III IV V VI VII

5 9701/32/M/J/16 © UCLES 2016 [Turn over (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of sodium hydroxide, NaOH, in the volume of FB 3 you calculated in (b). moles of NaOH = … mol (ii) Use your answer to (i) to calculate the number of moles of sulfuric acid present in the 25.0 cm3 of FB 4 pipetted in (a). moles of H2SO4 = … mol (iii) Use your answer to (ii) to calculate the number of moles of sulfuric acid, H2SO4, remaining in flask X after the reaction in 1(a). moles of H2SO4 remaining from 1(a) = … mol (iv) Use the relevant information on page 2 to calculate the number of moles of sulfuric acid, H2SO4, pipetted into reaction flask X in 1(a). moles of H2SO4 pipetted into flask X = … mol

6 9701/32/M/J/16 © UCLES 2016 (v) Use your answers to (iii) and (iv) to calculate the number of moles of sulfuric acid which reacted with the magnesium in flask X. moles of H2SO4 which reacted in flask X = … mol (vi) Use your answer to (v) and the mass of magnesium used in 1(a) to calculate the relative atomic mass, Ar, of magnesium. Ar of magnesium = … [6] (d) (i) A student, who carried out the experiments in Questions 1 and 2 correctly, calculated the Ar of magnesium as shown in the table. Question 1 Question 2 Ar Mg 20.8 22.5 Use the Ar of magnesium given in the Periodic Table on page 12 to deduce which practical procedure is less accurate. Identify one source of inaccuracy and explain one change the student could make in order to improve the accuracy. … is less accurate source of inaccuracy … … improvement … … (ii) Use the Ar of magnesium given in the Periodic Table to calculate the percentage error in the student’s value from Question 1. … … … [3] [Total: 17]

7 9701/32/M/J/16 © UCLES 2016 [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 identified by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. 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.

8 9701/32/M/J/16 © UCLES 2016 (a) (i) FB 5 is a solid element and FB 6 is a solid compound containing one cation and one anion. Carry out the following tests and record your observations. test observations Place a small spatula measure of FB 5 in a boiling tube, add a 1 cm depth of dilute hydrochloric acid and warm the contents of the tube gently. Place small spatula measures of FB 5 and FB 6 in a single boiling tube. Use a test-tube holder to hold the tube. Add a 2 cm depth of aqueous sodium hydroxide. CARE Place a spatula measure of FB 6 in a test-tube. Add a 3 cm depth of distilled water to form a solution for the following two tests. To a 1 cm depth of aqueous FB 6 in a test-tube add a 1 cm depth of dilute hydrochloric acid. To a 1 cm depth of aqueous FB 6 in a test-tube add aqueous sodium hydroxide. (ii) Suggest the identities of FB 5 and FB 6 from your observations. Refer to the relevant observations in your answers. FB 5: … reason(s) … … FB 6: cation … reason(s) … … anion … reason(s) … … … [9]

9 9701/32/M/J/16 © UCLES 2016 [Turn over (b) (i) FB 7 and FB 8 are solutions which contain different anions. These may be carbonate, halide, sulfate or sulfite. You are to devise tests to identify the two anions present. Record in a suitable table below: • the reagent(s) you use for each test, • the observations you make on carrying out the test, • the conclusion you make from the result of the test. (ii) The cation in either FB 7 or FB 8 is a transition metal ion. Carry out the following test to identify this cation and record your observations. test observations FB 7 FB 8 To a 1 cm depth of solution in a test-tube add aqueous sodium hydroxide. FB … contains the transition metal ion … . [9] [Total: 18]

10 9701/32/M/J/16 © UCLES 2016 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) 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 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 9701/32/M/J/16 © UCLES 2016 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) 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

12 9701/32/M/J/16 © UCLES 2016 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 –

® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 7 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/32 Paper 3 Advanced Practical Skills 2 May/June 2016 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 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 32 © Cambridge International Examinations 2016 Question Indicative material Mark Total 1 (a) I Appropriate headings and units for • mass of FB 1 • initial and final volumes (of gas). • unit: / g, (g), in g and allow grams / grammes for g and / cm3, (cm3), in cm3 or cm3 (for each heading) 1 II Award if candidate volume within appropriate range derived from Supervisor value 1 [2] (b) (i) Correctly calculates ( ) × V 24.0 1000 a 1 (ii) Correct expression mass Mg in a( ) b( ) i( ) 1 Both answers in (b) to 2 to 4 significant figures 1 [3] Question 1 [5]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 32 © Cambridge International Examinations 2016 2 (a) I Initial and final readings and titre value given for rough titre and initial and final readings for two (or more) accurate titrations (minimum of 2 x 2 box) 1 II Titre values recorded for accurate titrations and Appropriate headings for the accurate titration table and cm3 units. • initial / start burette reading / volume / value • final / end burette and reading / volume / value • titre or volume / FA3 and used / added • unit: / cm3 or (cm3) or in cm3 or cm3 (for each heading) 1 [7] III All accurate burette readings 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) 1 IV There are two (or more) uncorrected, accurate titres within 0.10 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 two initial titres, unless a further titration, within 0.10 cm3 of any other, has also been carried out. • Do not award the mark if any “accurate” burette readings (apart from initial 0 cm3) are given to zero dp. 1 V, VI and VII Examiner rounds any accurate burette to the nearest 0.05 cm3, checks subtractions and then select 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 titre, expressed to nearest 0.01 cm3. Accuracy marks are awarded as shown. Award V, VI and VII for δ ⩽ 0.30 (cm3) Award V and VI for 0.30 cm3 < δ ⩽ 0.60 (cm3) Award V for 0.60 cm3 < δ ⩽ 1.00 (cm3) 3

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 32 © Cambridge International Examinations 2016 (b) Candidate must take the average of two (or more) titres that are within a total spread of not more than 0.20 cm3. Working must be shown or ticks must be put next to the two (or more) accurate readings selected. The mean should be quoted to 2 dp, rounded to the nearest 0.01. Two special cases where the mean may not be to 2 dp: • Allow mean expressed to 3 dp only for 0.025 or 0.075 (e.g. 26.325) • Allow mean if expressed 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 allowed) (e.g. 26.0 and 26.1 = 26.1 is incorrect – should be 26.05.) 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 n(NaOH) 0.150 × b( ) 1000 1 (ii) (iii) Correctly uses (i) / 2 and (ii) × 10 1 (iv) Correctly calculates 1.00 × 25.0 / 1000 = 0.025(0) 1 (v) Correctly uses (c)(iv) – (c)(iii) 1 (vi) Correctly uses mass Mg in 1 a( ) v( ) 1 All final answers to 3 or 4 significant figures (minimum of four parts must be attempted) 1 [6]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 32 © Cambridge International Examinations 2016 (d) (i) (Experiment 1 is less accurate) One set of: Inaccuracy Improvement Inaccuracy • gas escaped before bung inserted Improvement • viable means of keeping solid and acid separate before being added (not put on lid faster) e.g. use divided flask • use more (excess) of a lower concentration of acid Inaccuracy • balance imprecise / inaccurate balance Improvement • use a balance calibrated to more decimal places (owtte) Inaccuracy • If candidate volume greater than 250 cm3 then allow problem of measuring volume of gas Improvement • use larger (capacity) measuring cylinder • use less / smaller mass Mg 1 1 [3] (ii) Correct expression or correctly calculates − 24.3 20.8 24.3 = 14.4% 1 Question 2 [17]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 32 © Cambridge International Examinations 2016 FB 5 is Al(s); FB 6 is NaNO3(s); FB 7 is Al 2(SO4)3(aq); FB 8 is MnCl 2(aq); 3 (a) (i) FB 5 + HCl: effervescence / fizzing / bubbling gas pops with lighted splint 1 1 FB 5 + FB 6 + NaOH: vigorous / violent / exothermic / great / extreme / lots of and effervescence / fizzing / bubbling gas / NH3 turns (damp) red litmus (paper) blue 1 1 FB 6 + HCl: no reaction / no change / no gas / no ppt and FB 6 +NaOH: no reaction / no change / no ppt 1 (ii) FB 5 is Al (allow Zn) and Reason: effervescence / gives H2 / NH3 in test 1 and / or 2 1 FB 6 cation unknown or Ba2+ or NH4 + or any group 1 metal and reason: from no reaction with NaOH 1 anion: NO3 – / NO2 – (or both) reason: If NO3 – then NH3 with NaOH + Al and no reaction with HCl 1 1 [9] (b) (i) Clearly laid out test / observation / conclusion sections Layout has to show clearly where two reagents are used as part of the same test. 1 BaCl2 / Ba(NO3)2 and HCl / HNO3 AgNO3 and NH3 1 1 FB 7 only + Ba2+ white precipitate and insoluble in HCl or HNO3 1 FB 8 only + Ag+ white precipitate 1 FB 7 = sulfate / SO4 2– (allow from white precipitate with Ba2+) FB 8 = chloride / Cl – (allow from white precipitate with Ag+) 1 1

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 32 © Cambridge International Examinations 2016 (ii) Off-white / light / pale brown / buff / beige precipitate and darkening on standing with FB 8 Ignore observation with FB 7 1 FB 8 = Mn2+ / manganese(II) from some correct evidence 1 [9] Question 3 [18]