Cambridge A Level Chemistry 9701 — 2025 May/June Paper 3 · Variant 7

This document has 16 pages. Any blank pages are indicated. [Turn over Cambridge International AS & A Level CHEMISTRY 9701/37 Paper 3 Advanced Practical Skills 1 May/June 2025 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. * 7 8 6 0 1 9 2 4 1 9 * DC (KS) 357228 © UCLES 2025 Session Laboratory For Examiner’s Use 1 2 3 Total ,










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2 9701/37/M/J/25 © UCLES 2025 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 Hydrogen peroxide, H2O2, reacts rapidly with acidified potassium manganate(VII), KMnO4. 5H2O2(aq) + 2MnO4 –(aq) + 6H+(aq) 5O2(g) + 8H2O(l) + 2Mn2+(aq) You will determine the concentration of a solution of hydrogen peroxide. You will first dilute the solution and then carry out a titration with acidified potassium manganate(VII). FA 1 is aqueous hydrogen peroxide, H2O2. FA 2 is 0.0300 mol dm–3 potassium manganate(VII), KMnO4. FA 3 is 1.0 mol dm–3 sulfuric acid, H2SO4. (a) Method Dilution of FA 1 • Pipette 25.0 cm3 of FA 1 into the 250 cm3 volumetric flask. • Add distilled water to make 250 cm3 of solution. • Shake the flask thoroughly. • Label this diluted solution of hydrogen peroxide FA 4. Titration • Fill the burette with FA 2. • Rinse the 25.0 cm3 pipette with distilled water and then with FA 4. • Pipette 25.0 cm3 of FA 4 into a conical flask. • Use the 25 cm3 measuring cylinder to add 10 cm3 of FA 3 to the conical flask. • 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 your recorded results show the precision of your practical work. • Record, in a suitable form in the space for results, all your burette readings and the volume of FA 2 added in each accurate titration. Keep FA 1 for use in Questions 2 and 3. Keep FA 2 for use in Question 3. * 0000800000002 * ,










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3 9701/37/M/J/25 © UCLES 2025 [Turn over Results [7] (b) From your accurate titration results, calculate a suitable mean value to use in your calculations. Show clearly how you obtain the mean value. 25.0 cm3 of FA 4 required … cm3 of FA 2. [1] (c) Calculations (i) Give your answers to (c)(ii), (c)(iii) and (c)(iv) to an appropriate number of significant figures. [1] (ii) Calculate the amount, in mol, of manganate(VII) ions in the volume of FA 2 in (b). amount of MnO4 – = … mol [1] (iii) Calculate the amount, in mol, of hydrogen peroxide in 25.0 cm3 of FA 4. amount of H2O2 = … mol [1] (iv) Calculate the concentration, in mol dm–3, of hydrogen peroxide in FA 1. concentration of H2O2 in FA 1 = … mol dm–3 [1] I II III IV V VI VII * 0000800000003 * ,










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4 9701/37/M/J/25 © UCLES 2025 (d) A student suggests that the experiment would be more accurate if a 10 cm3 pipette is used to measure FA 3 in place of the measuring cylinder. State whether the student’s suggestion is correct. Explain your answer. Include a calculation as part of your explanation. … … … [2] [Total: 14] * 0000800000004 * ,










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5 9701/37/M/J/25 © UCLES 2025 [Turn over BLANK PAGE * 0000800000005 * ,










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6 9701/37/M/J/25 © UCLES 2025 2 You will now determine the concentration of a solution of hydrogen peroxide by a different method. Hydrogen peroxide decomposes slowly into water and oxygen at room temperature. This reaction is exothermic. When a catalyst is added, the decomposition is fast and there is a measurable temperature rise. H2O2(aq) H2O(l) + 1 2O2(g) ΔH = −98.2 kJ mol−1 FA 1 is aqueous hydrogen peroxide, H2O2. FA 5 is manganese(IV) oxide, MnO2. (a) Method Experiment 1 • Support one of the cups in the 250 cm3 beaker. • Use the 50 cm3 measuring cylinder to add 25.0 cm3 of FA 1 to the cup. • Place the thermometer in the FA 1 and tilt the cup, if necessary, so that the bulb of the thermometer is fully covered. Record the temperature in the space for results. • Add a heaped spatula measure of FA 5 to the solution in the cup. • Stir constantly until the maximum temperature is reached. Record this temperature. • Calculate and record the temperature rise. • Rinse and dry the thermometer. Experiment 2 • Support the second cup in the 250 cm3 beaker. • Use the 50 cm3 measuring cylinder to add 40.0 cm3 of FA 1 to the second cup. • Measure and record the initial temperature of the solution. • Add a heaped spatula measure of FA 5 to the solution in the second cup. • Stir constantly until the maximum temperature is reached. Record this temperature. • Calculate and record the temperature rise. Keep FA 5 for use in Question 3. Results [5] I II III IV V * 0000800000006 * ,










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7 9701/37/M/J/25 © UCLES 2025 [Turn over (b) Calculations (i) Calculate the energy change, in J, in Experiment 2. energy change = … J [1] (ii) Use the information given and your answer to (b)(i) to calculate the concentration, in mol dm–3, of hydrogen peroxide in FA 1. concentration of H2O2 in FA 1 = … mol dm–3 [2] (c) The concentration of hydrogen peroxide in FA 1 calculated using the method given for Question 1 is more accurate than that using the method given for Question 2. (i) Heat loss is a large source of error when carrying out the method for Question 2. Describe and explain the effect of heat loss on the value of the concentration of hydrogen peroxide calculated. … … … [1] (ii) A student suggests that calculating the concentration of hydrogen peroxide using the method in Question 2 would be less accurate when the concentration is lower. Suggest whether the student is correct. Explain your answer. … … [1] [Total: 10] * 0000800000007 * ,










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8 9701/37/M/J/25 © UCLES 2025 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) Transfer a 2 cm depth of FA 2, KMnO4, into a test-tube. Add the same volume of aqueous sodium hydroxide followed by a small spatula measure of FA 5, MnO2. Stir for approximately 30 seconds then filter the mixture into a second test-tube. observations … … Add dilute sulfuric acid to the filtrate until no further change. observations … … [2] (ii) Transfer a 1 cm depth of aqueous iron(II) sulfate into a boiling tube. Add the same depth of dilute sulfuric acid followed by a very small spatula measure of FA 5, MnO2. Carefully warm the mixture using a Bunsen burner for about 20 seconds. Filter the warm mixture into a test-tube. observations … … Add aqueous sodium hydroxide dropwise to the filtrate until no further change. observations … … [2] * 0000800000008 * ,










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9 9701/37/M/J/25 © UCLES 2025 [Turn over (iii) Suggest a conclusion about the chemical behaviour of FA 5 using your observations in (a)(ii). FA 5 is acting as … [1] (iv) Write an ionic equation for the reaction between aqueous sodium hydroxide and the filtrate in (a)(ii). Include state symbols. … [1] Question 3 continues on page 10. * 0000800000009 * ,










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10 9701/37/M/J/25 © UCLES 2025 (b) FA 6 and FA 7 are both aqueous solutions of salts. Neither solution includes an ion that contains sulfur. FA 6 contains two cations and one anion. Two of the ions are listed in the Qualitative analysis notes. FA 7 contains one cation and one anion. One of the ions is listed in the Qualitative analysis notes. (i) Carry out the following tests and record your observations in Table 3.1. Use a 1 cm depth of FA 6 or FA 7 in a boiling tube for Test 1. Use a 1 cm depth of FA 6 or FA 7 in a test-tube for Tests 2, 3 and 4. Table 3.1 test observations FA 6 FA 7 Test 1 Add aqueous sodium hydroxide, then warm gently. Test 2 Add acidified aqueous KMnO4 dropwise until no further change. Test 3 Add an equal volume of FA 1, H2O2, then add a few drops of starch solution. Test 4 Add aqueous sodium carbonate. [6] * 0000800000010 * ,










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11 9701/37/M/J/25 © UCLES 2025 (ii) The anion in FA 6 does not contain nitrogen. Select one further reagent to identify the anion present in FA 6. Carry out a test with this reagent and record your observations in Table 3.2. Table 3.2 reagent observations [1] (iii) Give the formulae of the ions present in FA 6 and FA 7. If you are unable to identify an ion from your tests, write ‘unknown.’ The ions present in FA 6 are … and … and … . The ions present in FA 7 are … and … . [3] [Total: 16] * 0000800000011 * ,









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14 9701/37/M/J/25 © UCLES 2025 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+ * 0000800000014 * ,









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15 9701/37/M/J/25 © UCLES 2025 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 = 6.02 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 at 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) * 0000800000015 * ,









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16 9701/37/M/J/25 © UCLES 2025 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. * 0000800000016 * ,









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This document consists of 13 printed pages. © Cambridge University Press & Assessment 2025 [Turn over Cambridge International AS & A Level CHEMISTRY 9701/37 Paper 3 Advanced Practical Skills 1 May/June 2025 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 May/June 2025 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 2 of 13 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.

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 3 of 13 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.

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 4 of 13 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.

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 5 of 13 Annotations guidance for centres Examiners use a system of annotations as a shorthand for communicating their marking decisions to one another. Examiners are trained during the standardisation process on how and when to use annotations. The purpose of annotations is to inform the standardisation and monitoring processes and guide the supervising examiners when they are checking the work of examiners within their team. The meaning of annotations and how they are used is specific to each component and is understood by all examiners who mark the component. We publish annotations in our mark schemes to help centres understand the annotations they may see on copies of scripts. Note that there may not be a direct correlation between the number of annotations on a script and the mark awarded. Similarly, the use of an annotation may not be an indication of the quality of the response. The annotations listed below were available to examiners marking this component in this series. Annotations Annotation Meaning Correct point or mark awarded Incorrect point or mark not awarded Information missing or insufficient for credit Benefit of the doubt given Contradiction in response otherwise markworthy, mark not given Error in number of decimal places Error carried forward applied Incorrect or insufficient point ignored while marking the rest of the response Benefit of the doubt not applied in this instance

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 6 of 13 Annotation Meaning Rounding error Repeat error or / Blank page or part of script seen Error in number of significant figures Transcription error

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 7 of 13 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 Titre values recorded for accurate titrations, AND correct headings and units in the accurate titration table • initial / start AND (burette) reading / volume • final / end AND (burette) reading / volume • titre OR volume used / added OR FA 2 used / added • unit: / cm3 OR (cm3) OR in cm3 (for each heading) OR cm3 unit given for each volume recorded. 1 III All accurate burette readings recorded to 0.05 cm3. 1 IV The final accurate titre recorded must be within 0.10 cm3 of any other accurate titre. 1 Accuracy (Q) marks Round burette readings to the nearest 0.05 cm3. Check and correct titre subtractions where necessary. Select the best mean titre, using the following hierarchy: • two (or more) accurate identical titres (ignoring any that are labelled ‘rough’), then • two (or more) accurate titres within 0.05 cm3, then • two(or more) accurate titres within 0.10 cm3, etc. Calculate the candidate’s mean value. Calculate the difference () between the candidate’s mean titre and the supervisor’s mean titre. Award accuracy Q marks as follows: V Award if  ⩽ 0.80 cm3 VI Award if  ⩽ 0.50 cm3 VII Award if  ⩽ 0.30 cm3 3

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 8 of 13 Question Answer Marks 1(b) Correct calculation of the mean titre • Candidate must take the average of two (or more) 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.. 1 1(c)(i) Significant figures All answers in (c)(ii) – (c)(iv) are expressed to 3 or 4 sf. 1 1(c)(ii) Correctly calculates amount of MnO4− = ((b) / 1000)  0.03 mol 1 1(c)(iii) Correctly uses amount of H2O2 = (c)(ii)  2.5 mol 1 1(c)(iv) Correctly uses [H2O2] = (c)(iii)  40  10 mol dm−3 1 1(d) M1 Student is not correct AND acid is in excess M2 Calculation to show n(H+) added = 0.02 mol AND calculation of n(H+) required = (c)(ii)  3 OR = (c)(iii)  1.2 AND n(H+) added more than / greater than / in excess of n(H+) required. 2

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 9 of 13 Question Answer Marks 2(a) I Recording of results in the space for results Unambiguous headings AND units for all recorded results: • initial / FA 1 temperature / temp / T; • final / maximum temperature / temp / T • temp(erature) change / rise / T • Units: (°C) / / °C with each heading OR °C with each piece of data. II initial and final temperatures recorded for both experiments. AND clear indication of Experiments 1 and 2. III All thermometer readings recorded to nearest .5 °C AND temperature changes correctly calculated. IV Difference in temperature changes for Exps 1 and 2 are within the following ranges of the candidate’s mean T: Cand mean T ⩽ 5.0 5.25 – 10.0 10.25 – 15.0 ⩾ 15.25 T1 – T2| ⩽0.5 ⩽1.0 ⩽1.5 ⩽2.0 V Difference between mean temperature change for candidate and supervisor rounded to the nearest 0.5 ºC,  Sup mean T ⩽ 5.0 5.25 – 10.0 10.25 – 15.0 15.25 – 20.0 20.25 – 25.0  ⩽1.0 ⩽1.5 ⩽2.5 ⩽3.5 ⩽4.5 5 2(b)(i) Correctly calculates Energy change = 40  4.18  T for Exp 2. AND answer given to 2–4 sf. 1

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 10 of 13 Question Answer Marks 2(b)(ii) M1 Correctly uses [H2O2] = (b)(i) / (98.2  40) M2 Correct answer with some working shown OR some correct working which includes: (b)(i) / 98.2 OR (b)(i) / 98 200 OR (b)(i) / 3928 AND answer given to 2–4 sf 2 2(c)(i) Concentration will be lower AND two of: • T / maximum temp will be lower • (calculated / apparent) energy released / change will be lower • amount / moles (of FA 1 / H2O2) will be lower 1 2(c)(ii) The student is correct AND T will be lower AND (%) error will be greater OR The student is correct AND the experiment will be slower AND more time for heat to escape OR The student is not correct AND T will be lower AND heat loss will be less OR Student is not correct AND T will be lower AND this is cancelled out by a slower reaction. 1

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 11 of 13 Question Answer Marks FA 2 is KMnO4(aq); FA 5 is MnO2; FA 6 is FeCl3; FA 7 is KI 3(a)(i) M1 filtrate / solution AND (dark) green M2 (green) solution OR turns AND pink / purple 2 3(a)(ii) M1 filtrate / solution AND yellow / (pale) brown M2 red-brown / brown ppt (with NaOH) AND insoluble in excess 2 3(a)(iii) oxidising agent / oxidant 1 3(a)(iv) Fe3+(aq) + 3OH−(aq) → Fe(OH)3(s) OR H+ (aq) + OH- (aq) → H2O (l) 1

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 12 of 13 Question Answer Marks 3(b)(i) 2 * = 1 mark (round down). FA 6 (FeCl3) FA 7 (KI) Test 1 + NaOH (aq) Red-brown / brown / rust ppt * insoluble in excess * No change/ no ppt AND Heat No change / red litmus does not turn blue AND No change / red litmus does not turn blue * Test 2 + acidified KMNO4(aq) No change / purple colour / solution remains * (mixture/solution) turns brown / red-brown * Test 3 + FA 1, H2O2, then solution turns yellow / red-brown / brown * Effervescence / fizzing / bubbling* (gas / O2) relights a glowing splint* + starch solution dark blue / blue-black / black * Test 4 + Na2CO3(aq) Effervescence * Gas / CO2 / fizz forms white ppt with limewater * Red-brown / orange-brown / brown ppt. * No change * 6 3(b)(ii) silver nitrate / AgNO3 AND white ppt 1

9701/37 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2025 © Cambridge University Press & Assessment 2025 Page 13 of 13 Question Answer Marks 3(b)(iii) FA 6: Fe3+, H+, Cl– FA 7: I–, unknown 2 or 3 correct = 1 mark 4 correct = 2 marks 5 correct = 3 marks 3