Cambridge A Level Chemistry 9701 — 2024 Oct/Nov Paper 3 · Variant 4

This document has 12 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level CHEMISTRY 9701/34 Paper 3 Advanced Practical Skills 2 October/November 2024 2 hours You must answer on the question paper. You will need: The materials and apparatus listed in the confidential instructions INSTRUCTIONS ● Answer all questions. ● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. ● Write your name, centre number and candidate number in the boxes at the top of the page. ● Write your answer to each question in the space provided. ● Do not use an erasable pen or correction fluid. ● Do not write on any bar codes. ● You may use a calculator. ● You should show all your working and use appropriate units. INFORMATION ● The total mark for this paper is 40. ● The number of marks for each question or part question is shown in brackets [ ]. ● The Periodic Table is printed in the question paper. ● Important values, constants and standards are printed in the question paper. ● Notes for use in qualitative analysis are provided in the question paper. * 0 3 8 1 6 7 4 4 7 2 * DC (PQ) 326184/3 © UCLES 2024 Session Laboratory For Examiner’s Use 1 2 3 Total ,










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2 9701/34/O/N/24 © UCLES 2024 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 the precision of the apparatus you used in the data you record. Show your working and appropriate significant figures in the answer to each step of your calculations. 1 Iodine reacts with propanone in the presence of an acid catalyst. The rate of this reaction can be measured by determining how the concentration of iodine in the reaction mixture changes with time. CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq) A student studies this reaction by mixing together the following three solutions and immediately starting the stop-clock. ● 100.0 cm3 of 0.1000 mol dm–3 iodine, I2 ● 50.0 cm3 of 1.00 mol dm–3 propanone, CH3COCH3 ● 50.0 cm3 of 1.00 mol dm–3 sulfuric acid, H2SO4 The student removes 25.0 cm3 of the solution. After 80 seconds, 50.0 cm3 of a solution of sodium hydrogencarbonate, NaHCO3, is added which reacts with all the sulfuric acid in the sample. Distilled water is added until the volume of the solution is 150.0 cm3. This solution is FB 1. In this experiment you will determine the concentration of iodine in FB 1 and so determine the average rate of reaction during the first 80 seconds. You will do this by titration using sodium thiosulfate solution. I2(aq) + 2S2O3 2–(aq) 2I–(aq) + S4O6 2–(aq) FB 1 is a sample of the solution prepared by the student. FB 2 is 0.0100 mol dm–3 sodium thiosulfate, Na2S2O3. FB 3 is starch indicator. (a) Method ● Fill the burette with FB 2. ● Pipette 25.0 cm3 of FB 1 into a conical flask. ● Run FB 2 into the conical flask until the colour of the solution turns yellow. Then add 10 drops of FB 3. The solution will turn blue-black. ● The end-point of the titration is when the solution turns colourless. ● 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. ● Make sure any recorded results show the precision of your practical work. ● Record all your burette readings and the volume of FB 2 added in each accurate titration. * 0000800000002 * ,










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3 9701/34/O/N/24 © UCLES 2024 [Turn over Results I II III IV V VI VII [7] (b) From your accurate titration results, calculate a suitable mean value to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FB 1 required … cm3 of FB 2. [1] (c) Calculations (i) Give your answers to each part of (c)(ii) and (c)(iii) to an appropriate number of significant figures. [1] (ii) Use your answer to (b) to calculate the amount, in mol, of thiosulfate ions in your mean titre. amount of S2O3 2– = … mol Hence calculate the amount, in mol, of iodine present in the total volume of 150.0 cm3 that the student prepares. amount of I2 = … mol [2] (iii) Calculate the concentration, in mol dm–3, of iodine in the sample that the student removes from the reaction mixture. concentration of I2 = … mol dm–3 [1] * 0000800000003 * ,










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4 9701/34/O/N/24 © UCLES 2024 (iv) Calculate the initial concentration of iodine in the reaction mixture. (If you were unable to determine an answer to (c)(iii) use 0.0315 mol dm–3 as the concentration of I2 in the sample the student removed.) initial concentration of I2 = … mol dm–3 Hence calculate the average rate of reaction during the first 80 seconds using the formula shown. average rate of reaction = change in the concentration of I2 time average rate = … … value units [2] (d) Suggest why the starch solution is added when the solution in the conical flask turns yellow and not added at the start of the titration. … … [1] (e) A student suggests that the experimental procedure is incorrect. The student says that the sample should be removed from the reaction mixture at 80 seconds rather than the sodium hydrogencarbonate being added at 80 seconds. State if you agree with this student. Explain your answer. … … … [1] [Total: 16] * 0000800000004 * ,










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5 9701/34/O/N/24 © UCLES 2024 [Turn over 2 In this experiment you will identify the ions in the hydrated salt MA2•2H2O, where M is a Group 2 metal. You will first determine the relative formula mass of the salt by measuring the mass loss when the sample is heated. Heating the sample produces the anhydrous salt and water of crystallisation. You will then select reagents to determine the identity of the ion A–. FB 4 is the salt, MA2•2H2O. (a) Method ● Weigh the empty crucible with its lid. Record the mass. ● Transfer all of FB 4 into the crucible. ● Weigh the crucible, lid and FB 4. Record the mass. ● Calculate and record the mass of FB 4 used. ● Place the crucible and contents on a pipe-clay triangle. ● Heat the crucible gently, with the lid on, for approximately 1 minute. ● Heat strongly, with the lid off, for a further 4 minutes. ● Replace the lid and leave the crucible to cool for at least 5 minutes. While the crucible is cooling, you may wish to begin work on Question 3. ● When the crucible has cooled, weigh the crucible with its lid and contents. Record the mass. ● Heat strongly, with the lid off, for a further 2 minutes. ● Replace the lid and leave the crucible to cool for at least 5 minutes. ● When the crucible has cooled, reweigh the crucible with its lid and contents. Record the mass. ● Calculate and record the mass of residue obtained. Results I II III IV V [5] (b) Calculate the amount, in mol, of water lost. amount of H2O = … mol Hence calculate the relative formula mass, Mr, of MA2. Mr of MA2 = … [2] * 0000800000005 * ,










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6 9701/34/O/N/24 © UCLES 2024 (c) FB 5 is a solution of the hydrated salt MA2. The A– ion is a halide. Carry out tests to identify the halide present in MA2. Record the reagents used, the results of your tests and the identity of A–. A– is … [2] (d) Using your answers to (b) and (c), identify the ion M2+. M2+ is … [1] (e) A student correctly identifies A– but did not heat the sample of FB 4 for long enough to remove all the water of crystallisation. Despite this error, the student still correctly identifies M2+. Explain how the student’s answer in (b) would differ from the true answer. … … Explain why the student still correctly identifies M2+. … … [2] [Total: 12] * 0000800000006 * ,










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7 9701/34/O/N/24 © UCLES 2024 [Turn over Qualitative analysis For each test you should record all your observations in the spaces provided. Examples of observations include: ● colour changes seen ● the formation of any precipitate and its solubility (where appropriate) in an excess of the reagent added ● the formation of any gas and its identification (where appropriate) by a suitable test. You should record clearly at what stage in a test an observation is made. Where no change is observed, you should write ‘no change’. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. If any solution is warmed, a boiling tube must be used. If a solid is heated, a hard-glass test-tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests should be attempted. 3 (a) (i) FB 6 is potassium manganate(VII). Place all the FB 6 in a hard-glass test-tube and heat gently at first and then more strongly. Record your observations. … … … [1] Leave the tube to cool and keep for use in (a)(ii). While the tube is cooling, you may wish to begin work on (b). (ii) Complete Table 3.1 by carrying out the tests described. Record your observations. Table 3.1 test observations Test 1 To a 7 cm depth of distilled water in a boiling tube, add approximately half of the residue from (a)(i). Test 2 To a 4 cm depth of aqueous sodium hydroxide in a test-tube, add the remaining residue from (a)(i). [2] (iii) Suggest what type of reaction takes place in (a)(i). … [1] * 0000800000007 * ,










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8 9701/34/O/N/24 © UCLES 2024 (b) FB 7 is a solution of a salt which contains a cation and an anion from those listed in the Qualitative analysis notes. FB 8 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. (i) Complete Table 3.2 by carrying out the tests described. Record your observations. Table 3.2 test observations Test 1 To a 1 cm depth of FB 7 in a test-tube, add aqueous ammonia until there is no further change, then add a few drops of hydrogen peroxide. Test 2 To a 1 cm depth of FB 7 in a test-tube, add a 1 cm depth of aqueous potassium iodide, then add FB 8. [5] (ii) The anion in FB 7 is either the sulfite ion or the sulfate ion. Carry out tests to identify which ion is present. Record the reagents used and the results of your tests. [2] (iii) Give the formula of the salt in FB 7. … [1] [Total: 12] * 0000800000008 * ,










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10 9701/34/O/N/24 © UCLES 2024 Qualitative analysis notes 1 Reactions of cations cation 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 warming – barium, Ba2+(aq) faint white ppt. is observed unless [Ba2+(aq)] is very low no ppt. calcium, Ca2+(aq) white ppt. unless [Ca2+(aq)] is very low 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 pale 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 2 Reactions of anions anion 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 / off-white ppt. with Ag+(aq) (partially soluble in NH3(aq)) iodide, I–(aq) gives pale 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; decolourises acidified aqueous KMnO4 sulfate, SO4 2–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids); gives white ppt. with high [Ca2+(aq)] sulfite, SO3 2–(aq) gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids); decolourises acidified aqueous KMnO4 thiosulfate, S2O3 2–(aq) gives off-white/pale yellow ppt. slowly with H+ * 0000800000010 * ,










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11 9701/34/O/N/24 © UCLES 2024 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 hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint 4 Tests for elements element test and test result iodine, I2 gives blue-black colour on addition of starch solution Important values, constants and standards molar gas constant R = 8.31 J K–1 mol–1 Faraday constant F = 9.65 × 104 C mol–1 Avogadro constant L = 6.022 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 s.t.p. (101 kPa and 273 K) Vm = 24.0 dm3 mol–1 at room conditions ionic product of water Kw = 1.00 × 10–14 mol2 dm–6 (at 298 K (25 °C)) specific heat capacity of water c = 4.18 kJ kg–1 K–1 (4.18 J g–1 K–1) * 0000800000011 * ,









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12 9701/34/O/N/24 © UCLES 2024 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 – 113 Nh nihonium – 115 Mc moscovium – 117 Ts tennessine – 118 Og oganesson – 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 144.2 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 – To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. * 0000800000012 * ,









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This document consists of 10 printed pages. © Cambridge University Press & Assessment 2024 [Turn over Cambridge International AS & A Level CHEMISTRY 9701 / 34 Paper 3 Advanced Practical Skills 2 October/November 2024 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 2024 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 2 of 10 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 descriptions 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 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 3 of 10 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. Science-Specific Marking Principles 1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks should not be awarded if the keywords are used incorrectly. 2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored. 3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection). 4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where necessary and any exceptions to this general principle will be noted. 5 ‘List rule’ guidance For questions that require n responses (e.g. State two reasons …): • The response should be read as continuous prose, even when numbered answer spaces are provided. • Any response marked ignore in the mark scheme should not count towards n. • Incorrect responses should not be awarded credit but will still count towards n. • Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should be treated as a single incorrect response. • Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 4 of 10 6 Calculation specific guidance Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show your working’. For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values. For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1 and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme. Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded. Exceptions to this general principle will be noted in the mark scheme. 7 Guidance for chemical equations Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme. State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 5 of 10 Question Answer Marks 1(a) I All the following data are recorded • two burette readings and titre for the rough titration • initial and final burette readings for two (or more) accurate titrations 1 II Correct headings and units shown in the accurate titration table and titre values recorded for accurate titrations • initial / start and (burette) reading / volume • final / end and (burette) reading / volume • titre or volume / FB 2 and used / added • unit: / cm3 or (cm3) or in cm3 (for each heading) or cm3 unit given for each volume recorded 1 Ill All accurate burette readings are recorded to the nearest 0.05 cm3. 1 lV: The final accurate titre recorded is within 0.10 cm3 of any other accurate titre 1 Award accuracy Q marks as follows: V Award if  ⩽ 0.60 cm3 VI Award if  ⩽ 0.40 cm3 VII Award if  ⩽ 0.20 cm3 If Supervisor’s mean titre > 50.00 cm3 then use the tolerances (0.80, 0.50, 0.30 cm3) If Supervisor’s mean titre < 10.00 cm3 then halve the tolerances (0.30, 0.20, 0.10 cm3) If Supervisor’s mean titre < 5.00 cm3 then use the tolerances (0.15, 0.10, 0.05 cm3) 1 1(b) Correctly calculates the mean titre to 2 decimal places. • Candidate must take the average of two (or more) accurate titres that are within a total spread of not more than 0.20 cm3. • Working / explanation must be shown or ticks must be put next to the two (or more) accurate readings selected. • The mean should be quoted to 2 d.p. and be rounded to nearest 0.01 cm3. (e.g. 26.675 cm3 must be rounded to 26.68 cm3). 1

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 6 of 10 Question Answer Marks 1(c)(i) Answers to all 3 parts of (c)(ii) and (c)(iii) quoted to 3 or 4 significant figures. 1 1(c)(ii) M1: Correctly calculates amount of S2O32– = (b) / 1000  0.0100 (1) M2: Correct use of n(S2O32–) amount of I2 = ans / 2  150 / 25 (1) 2 1(c)(iii) Correct use of amount of I2 from (c)(ii) / 0.150 or (M1 from (c)(ii) / 2)  (1000 / 25) 1 1(c)(iv) M1: Correctly calculates 0.05(00) and correctly uses (0.0500 – (c)(iii)) / 80 M2: Units mol dm–3 s–1 2 1(d) Release of iodine from the starch complex is slow at high iodine concentrations Or A starch-iodine complex / precipitate is formed which does not decompose (during the titration) 1 1(e) The student is incorrect and one of: • The sodium hydrogencarbonate must be added at 80 s to stop / quench the reaction (by reacting with the acid catalyst) ORA • The reaction would continue if the sodium hydrogencarbonate is not added at 80 s • The sample can be removed before 80 s as the reaction only stops when the sodium hydrogencarbonate is added. • The sodium hydrogencarbonate reacts with the acid which is the catalyst. 1

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 7 of 10 Question Answer Marks 2(a) I 4 unambiguous headings for balance readings and correct units • (Mass of) crucible + lid • (Mass of) crucible, lid and FB 4 (or ‘contents before heating’) • (Mass of) crucible, lid and contents / residue after first heating • (Mass of) crucible, lid and contents / residue after second heating Units with all required headings: / g, (g), in g (or g with every entry) 1 II Recording of all weighings • All 4 weighings recorded to same number of decimal places (two or three). • Fourth weighing is within +0.02 and –0.05 g of third weighing. 1 III Calculated masses Correct subtractions to give masses of FB 4 and residue and both headings clearly labelled and both answers to min 2 sf. 1 For assessment of accuracy (Q) marks Calculate the candidate’s mass ratio (to 2 d.p.) = mass FB 4 / mass of residue. If 4th weighing > 3rd weighing, use lower value to calculate the mass of residue. Award accuracy Q marks as follows: Award IV if 1.07 ≤ ratio ≤ 1.27 Award V if 1.12 ≤ ratio ≤ 1.22 2

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 8 of 10 Question Answer Marks 2(b) M1 Correctly calculates amount of water amount of H2O = (mass of FB 4 – mass of residue) / 18 and answer to 2–4 s.f. M2 Correct use of amount of water Mr of MA2 = 2  mass of residue / amount of H2O and answer to 2–4 s.f. 2 2(c) Identification of A− • use of (aqueous) silver nitrate / AgNO3 • white precipitate formed • precipitate is soluble in (excess aqueous) ammonia • A− is identified as Cl − / chloride 2 2(d) Identification of M2+ Shows working: ((b) – 71) and selects M from Group 2 with closest Ar and 2+ charge on ion 1 2(e) M1 (Calculated) Mr would be greater and amount / moles of water is smaller or mass of residue / MA2 is greater 1 M2 One of: • there are significant / big differences between the Ar s of the elements / metals (in Group 2) owtte • most of the water was driven off / very little water of crystallisation left owtte • the calculated Ar (or Mr) is still closest to the same answer 1

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 9 of 10 Question Answer Marks Q3 FB 6 is KMnO4; FB 7 is CuSO4(aq) 3(a)(i) 2* = 1 mark • (Dark) purple / purple-black solid / crystals (initially) • (Solid / crystals) jump(s) around the tube / pops / crackles (on heating) • Black powder / solid / residue (remains) • (gas) relights a glowing splint • (gas produced is) oxygen 1 3(a)(ii) Test 1 (forms) purple solution Or (water) turns purple (solution) 1 Test 2 (forms) green solution or (NaOH) turns green (solution) 1 3(a)(iii) thermal decomposition / redox 1

9701 / 34 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2024 © Cambridge University Press & Assessment 2024 Page 10 of 10 Question Answer Marks 3(b)(i) Observations Test Observations 1 +NH3 (pale) blue ppt * (ppt) soluble / disappears in excess (NH3) or solution formed in excess (NH3) * Deep / dark blue (solution) (with excess) * + H2O2 black / (dark) green* effervescence* (gas) relights a glowing splint* 2 + KI brown / yellow-brown / yellow solution* (off-)white / (pale) brown / yellow-brown precipitate / solid* + Na2S2O3 Solution / solid / ppt becomes paler owtte* Precipitate partially dissolves or ppt dissolves in excess (thiosulfate)* 5 3(b)(ii) M1 Choice of reagent(s) Selects barium chloride / BaCl2 or barium nitrate / Ba(NO3)2 and nitric acid / HNO3 or hydrochloric acid / HCl OR Selects (acidified aqueous) potassium manganate(VII) / (H+) & KMnO4 1 M2 Clear results to show: white ppt (with Ba2+) and insoluble in acid OR (KMnO4) remains purple / not decolourised / no change 1 3(b)(iii) CuSO4 1