Cambridge A Level Chemistry 9701 — 2016 Oct/Nov Paper 3 · Variant 1

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 9701/31 Paper 3 Advanced Practical Skills 1 October/November 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 11_9701_31/FP © UCLES 2016 *0163707882* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/31/O/N/16 © UCLES 2016 1 In Questions 1 and 2 you will determine the percentage purity of industrial grade calcium carbonate, CaCO3, 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 industrial grade calcium carbonate, in the form of small marble chips, and a known amount of dilute hydrochloric acid. The acid will be in excess. The impurities in the calcium carbonate will not react with the acid. CaCO3(s) + 2HCl (aq) → CaCl 2(aq) + H2O(l) + CO2(g) FA 1 is industrial grade calcium carbonate, CaCO3, in the form of small marble chips. FA 2 is 2.00 mol dm–3 hydrochloric acid, HCl. (a) Method Read through the whole method before starting any practical work. The diagram below may help you in setting up your apparatus. water clamp clamp X tub • 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 FA 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 container with FA 1 and record the mass in the space on page 3. • Remove the bung from the neck of the flask. Tip FA 1 into the acid 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. • Reweigh the container and any residue of FA 1 and record the mass in the space on page 3. • Calculate and record in the space on page 3 the mass of FA 1 used. • When no more gas is given off, measure and record the final volume of gas in the measuring cylinder in the space on page 3. Keep the contents of flask X for use in Question 2.

3 9701/31/O/N/16 © UCLES 2016 [Turn over Results [2] (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 carbon dioxide gas collected in the measuring cylinder. (Assume that 1 mole of gas occupies 24.0 dm3 under these conditions.) moles of CO2 = … mol (ii) Use your answer to (i) and the Periodic Table on page 12 to calculate the mass of pure calcium carbonate in the sample of industrial grade calcium carbonate, FA 1. mass of CaCO3 = … g (iii) Use your answer to (ii) and the mass of marble chips used in (a) to calculate a value for the percentage purity of the sample of industrial grade calcium carbonate, FA 1. percentage purity of FA 1 = … % [4] (c) Not all the carbon dioxide given off in the reaction is collected in the measuring cylinder. Suggest a change to the method which would lead to an increase in the volume of carbon dioxide collected. … … [1] [Total: 7]

4 9701/31/O/N/16 © UCLES 2016 2 You will determine the amount of hydrochloric acid remaining in flask X after the reaction with the marble chips in Question 1. You will do this by titration with sodium hydroxide of known concentration. NaOH(aq) + HCl (aq) → NaCl (aq) + H2O(l) The impurities in the calcium carbonate will not react with the alkali. FA 3 is 0.140 mol dm–3 sodium hydroxide, NaOH. bromophenol blue indicator (a) Method • Transfer all the contents of flask X 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 FA 4. • Rinse the pipette then use it to transfer 25.0 cm3 of FA 4 into a conical flask. • Add about 10 drops of bromophenol blue indicator. • Fill the burette with FA 3. • Perform 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. • Record, in a suitable form below, all of your burette readings and the volume of FA 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 FA 3 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FA 4 required … cm3 of FA 3. [1] I II III IV V VI VII

5 9701/31/O/N/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, present in the volume of FA 3 you calculated in (b). moles of NaOH = … mol (ii) Use your answer to (i) and the equation on page 4 to determine the number of moles of hydrochloric acid, HCl, present in the 25.0 cm3 of FA 4 pipetted in (a). moles of HCl = … mol (iii) Use your answer to (ii) to calculate the number of moles of hydrochloric acid, HCl, remaining in flask X after the reaction in 1(a). moles of HCl remaining = … mol (iv) Use the relevant information on page 2 to calculate the number of moles of hydrochloric acid, HCl, pipetted into flask X in 1(a). moles of HCl pipetted into flask X = … mol (v) Use your answers to (iii) and (iv) to calculate the number of moles of hydrochloric acid, HCl, which reacted with the marble chips in flask X. moles of HCl which reacted in flask X = … mol

6 9701/31/O/N/16 © UCLES 2016 (vi) Use your answer to (v), the equation in Question 1 and the Periodic Table on page 12 to calculate the mass of pure calcium carbonate, CaCO3, in the sample of industrial grade calcium carbonate, FA 1. mass of CaCO3 = … g (vii) Use your answer to (vi) and the mass of marble chips recorded in 1(a) to calculate the percentage purity of FA 1. percentage purity of FA 1 = … % [5] (d) You have carried out two different methods to find the percentage purity of industrial grade calcium carbonate. A source of error in Question 1 is that some carbon dioxide escapes before the bung can be inserted. How would this affect the percentage purity of FA 1 calculated in the two questions? Explain your answers. Question 1 … … … Question 2 … … … [3] [Total: 16]

7 9701/31/O/N/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. 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) FA 5 and FA 6 are solids each containing one cation and one anion. Carry out the following tests and record your observations in the table below. test observations FA 5 FA 6 (i) Place a spatula measure of solid in a hard-glass test-tube and heat gently at first, then heat strongly until no further change takes place. Leave the tube to cool completely then add a 2 cm depth of dilute sulfuric acid to the solid residue. Shake the contents of the tube then leave it to stand.

8 9701/31/O/N/16 © UCLES 2016 test observations FA 5 FA 6 (ii) Place a spatula measure of solid in a boiling tube and add a 2 cm depth of dilute sulfuric acid. Keep the solutions formed in (ii) for tests (iii) and (iv). (iii) To a 1 cm depth of solution from (ii) in a test-tube, add aqueous sodium hydroxide. (iv) To a 1 cm depth of solution from (ii) in a test-tube, add aqueous ammonia. (v) Identify as many ions as you can from your observations. Write ‘unknown’ where you have not been able to identify an ion. FA 5: cation … anion … FA 6: cation … anion … (vi) Write an equation, including state symbols, for the reaction between FA 6 and dilute sulfuric acid. … [12]

9 9701/31/O/N/16 © UCLES 2016 [Turn over (b) FA 7 is a solution containing one anion from those listed on page 11. The anion is either a halide or contains nitrogen. (i) You are to select suitable reagents to determine the identity of this anion. Record these in a suitable form below. (ii) Use these reagents to carry out tests to identify the anion in FA 7. Record your observations and conclusions in the space below. [5] [Total: 17]

10 9701/31/O/N/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) 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 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 9701/31/O/N/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 9701/31/O/N/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 9701/31 Paper 3 Advanced Practical Skills 1 October/November 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 October/November 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 – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks 1(a) I Correct headings and units for mass of FA 1 and volume of CO2 • Mass of container + FA 1 • Mass of container (+ residue) • Mass of FA 1 • Volume of gas Allow vol for volume but not V Units needed for all readings 1 II Both weighings to the same number of dp and correct mass of FA 1 calculated (If initial and final volumes recorded then subtraction for volume collected must be correct.) 1 2 1(b)(i) Correctly calculates ( ) × V 24.0 1 000 a 1 1(b)(ii) Correct expression (i) × 100.1 or (i) × (40.1 + 12 + (3)16) Must show working 1 1(b)(iii) Correctly uses ( ) ( ) x1 00 mass in ii a 1 All three answers to 2 to 4 sf 1 4 1(c) Any of: warm water in tub / saturate water with CO2 / a specific method of separation of CaCO3 and acid so only mixed after bung inserted / gas syringe 1 1 Total 7

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks 2(a) I Initial and final burette readings and volume added recorded for rough titre and accurate titre details tabulated. [minimum 2 × 2 ‘boxes’ with relevant information] 1 II Initial and final burette readings recorded and volume of FA 3 added recorded for each accurate titration. Headings and units correct for accurate titrations Headings: initial / final (burette) reading / volume or reading / volume at start / finish and volume / FA 3 added / used or titre [not difference/total] allow vol but not V 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(.0) 1 IV Final uncorrected titre is within 0.10 cm3 of any previous uncorrected accurate titre. Do not include a reading if it is labelled rough. Do not award the mark if any accurate burette readings (apart from the initial zero) are given as integers. 1

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks V, VI and VII Examiner rounds any accurate burette readings to the nearest 0.05 cm3, checks subtractions and then selects the ‘best’ accurate titres using the hierarchy: identical titres; titres within 0.05 cm3; titres within 0.1 cm3; etc., to calculate mean correct to 0.01 cm3. Examiner uses the best titre to calculate the ratio of acid remaining after reaction with calcium carbonate in Question 1 to this best titre from Question 2 for Supervisor and each candidate. The ratio of this value for the candidate is compared to the ratio of this value for the Supervisor and marks awarded as follows. Award V, VI and VII for 0.95 – 1.05 Award V and VI for 0.90 – 1.10 Award V for 0.80 – 1.20 3 7

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks 2(b) Check mean titre is correctly calculated from clearly selected values (ticks or working). • Candidate must average two (or more) 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 dp rounded to the nearest 0.01. [e.g. 26.667 must be rounded to 26.67] 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.] Do not award this mark if: • the rough titre was used to calculate the mean; • candidate carried out only 1 accurate titration; • burette readings were incorrectly subtracted to obtain any of the accurate titre values; • all burette readings (resulting in titre values used in calculation of mean) are integers. 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 2(c)(i) and (ii) Correctly calculates ( ) × 0.140 1000 b and same answer in (ii) and both answers to 3 or 4 sf 1 2(c)(iii) and 2(c)(iv) Correctly uses (ii) × 10 and Answer = 5.(00) × 10–2 1 2(c)(v) Correctly calculates (iv) – (iii) 1 2(c)(vi) Correctly uses [(v) × 100.1]/2 1

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks 2(c)(vii) Correctly uses [(vi) × 100)/(mass in (a)] to a minimum of 2 sf 1 5 2(d) Question 1: % purity lower as loss of gas means fewer moles / less mass CaCO3 1 1 Question 2: no change / % same as same amount of acid reacts / (amount) acid left is same 1 1 4 max 3 Total 16 Question Answer Marks FA 5 is NaNO3(s); FA 6 is CuCO3(s); FA 7 is NaBr(aq) 3(a)(i) FA 5 FA 6 (goes to) colourless or yellow liquid/ solution (green) powder / solid (turns) black / black residue gas relights glowing splint or gas turns limewater milky / cloudy white / chalky / forms white ppt gas (turns) brown / brown gas or solution turns blue (pale) blue solution / liquid formed 1+1 1 1+1

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9701 31 © UCLES 2016 Question Answer Marks 3(a)(ii)–(iv) FA 5 FA 6 (iii) solid dissolves / colourless solution allow no reaction / no change / no effervescence effervescence / fizzing / bubbling and blue solution / liquid formed (iv) no reaction / no change / no ppt / remains colourless blue ppt and insoluble in excess (v) no reaction / no change / no ppt / remains colourless (pale) blue ppt and soluble in excess to give deep / dark blue (solution) 1 1 1 3(a)(v) FA 5: cation unknown; anion nitrate / NO3 – FA 6: cation Cu2+ / copper(II); anion carbonate / CO3 2– 4 correct = 3 marks 3 correct = 2 marks 2 correct = 1 mark 1 1 1 3(a)(vi) CuCO3(s) + H2SO4(aq) → CuSO4(aq) + H2O(l) + CO2(g) 1 12 3(b)(i) Selects AgNO3 and NH3 Selects NaOH and Al and HCl / HNO3 / H2SO4 1 1 3(b)(ii) Clearly defined test | observation | conclusion sections FA 7 + AgNO3 cream ppt partially soluble in NH3 FA 7 is bromide / Br – from cream ppt 1 1 1 5 Total 17