Cambridge A Level Chemistry 9701 — 2025 Oct/Nov Paper 3 · Variant 5

This document has 12 pages. [Turn over Cambridge International AS & A Level CHEMISTRY 9701/35 Paper 3 Advanced Practical Skills 1 October/November 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. * 3 9 2 6 7 1 1 5 8 5 * DC (SL) 341188/3 © UCLES 2025 Session Laboratory For Examiner’s Use 1 2 3 Total ,










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2 9701/35/O/N/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 use in the data you record. Show your working and appropriate significant figures in the final answer to each step of your calculations. 1 Hydrated ethanedioic acid is a diprotic acid with the formula (COOH)2•xH2O where x is an integer. Ethanedioic acid reacts with manganate(VII) ions when heated. 5(COOH)2(aq) + 2MnO4 –(aq) + 6H+(aq) 10CO2(g) + 2Mn2+(aq) + 8H2O(l) You will determine the value of x in (COOH)2•xH2O by titrating a solution containing ethanedioic acid with manganate(VII) ions. ● FA 1 is 6.20 g dm–3 aqueous ethanedioic acid, (COOH)2•xH2O. ● FA 2 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4. ● FA 3 is 1.0 mol dm–3 sulfuric acid, H2SO4. (a) Method ● Fill the burette with FA 2. ● Pipette 25.0 cm3 of FA 1 into a conical flask. ● Use the measuring cylinder to add approximately 20 cm3 of FA 3 to the conical flask. ● Place the conical flask on a tripod and gauze and heat carefully until the temperature of the solution is approximately 70 °C. ● Remove the flame. ● Carefully lift the hot conical flask and place it on the white tile under the burette. ● Add FA 2 drop-wise for the first 2–3 cm3. Any initial pink colouring may take several seconds to disappear. ● If the reaction mixture turns brown, reheat it to about 70 °C. If the brown colour disappears, continue the titration. If the brown colour remains, discard the contents of the flask and begin a new titration. ● The end-point is reached when a permanent pale pink colour is formed. ● Perform a rough titration with FA 2. Record your burette readings in the space below. The rough titre is … cm3. ● Carry out as many 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 FA 2 added in each accurate titration. * 0000800000002 * ,










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3 9701/35/O/N/25 © UCLES 2025 [Turn over Results [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 FA 1 required … cm3 of FA 2. [1] I II III IV V VI VII * 0000800000003 * ,










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4 9701/35/O/N/25 © UCLES 2025 (c) Calculations (i) Give your answers to (c)(ii), (c)(iii) and (c)(iv) to the appropriate number of significant figures. [1] (ii) Calculate the amount, in mol, of manganate(VII) ions, MnO4 –, in the volume of FA 2 calculated in (b). amount of MnO4 – = … mol [1] (iii) Calculate the amount, in mol, of ethanedioic acid that reacts with the manganate(VII) ions in (c)(ii). amount of (COOH)2 = … mol Hence calculate the concentration, in mol dm–3, of ethanedioic acid in FA 1. concentration of (COOH)2 = … mol dm–3 [2] (iv) Calculate the relative molecular mass, Mr, of the ethanedioic acid in FA 1. Mr = … [1] (v) Calculate the value of x in (COOH)2•xH2O. Show your working. x = … [1] (d) Explain why it is necessary to add FA 3 in each titration. … … [1] [Total: 15] * 0000800000004 * ,










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5 9701/35/O/N/25 © UCLES 2025 [Turn over 2 Hydrated zinc sulfate has the formula ZnSO4•yH2O where y is an integer. Hydrated zinc sulfate decomposes when heated, losing only its water of crystallisation and becoming anhydrous. You will determine the value of y in ZnSO4•yH2O by heating the hydrated salt until it becomes anhydrous. FA 4 is hydrated zinc sulfate, ZnSO4•yH2O. (a) Method ● Weigh the crucible with its lid. Record the mass in the space for Results. ● Add between 3.20 g and 3.40 g of FA 4 to the crucible. ● Weigh the crucible with its lid and FA 4. Record the mass. ● Place the crucible on the pipeclay triangle. Gently heat the crucible and contents for approximately 2 minutes with the lid on. ● Remove the lid. Heat the crucible and contents strongly for approximately 4 minutes. ● Replace the lid and leave the crucible and residue to cool for at least 5 minutes. You may wish to begin work on Question 3 while the crucible is cooling. ● Weigh the crucible with its lid and its contents. Record the mass. ● Remove the lid. Heat the crucible strongly for approximately 3 minutes. ● Replace the lid and leave the crucible and residue to cool for at least 5 minutes. ● Weigh the crucible with its lid and its contents. Record the mass. ● Calculate the mass of FA 4 used and the mass of residue obtained. Record the masses. Results [5] I II III IV V * 0000800000005 * ,










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6 9701/35/O/N/25 © UCLES 2025 (b) Calculations (i) Calculate the amount, in mol, of anhydrous zinc sulfate residue formed in the decomposition of FA 4. amount of ZnSO4 = … mol Calculate the amount, in mol, of water of crystallisation lost. amount of H2O = … mol [2] (ii) Calculate the value of y in the formula ZnSO4•yH2O. Show your working. y = … [2] (c) A student suggests using this thermal decomposition method to investigate the number of moles of water of crystallisation in hydrated ethanedioic acid. The teacher says that this method is unsuitable. Suggest why this method is unsuitable. … … [1] [Total: 10] * 0000800000006 * ,










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7 9701/35/O/N/25 © UCLES 2025 [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) A bottle labelled FA 5 is thought to contain hydrated zinc sulfate. It would therefore contain zinc ions and sulfate ions as well as water of crystallisation. (i) Devise and carry out tests to investigate whether zinc ions, sulfate ions and water of crystallisation are present. Record the tests you carry out and the observations you see in the space provided. [5] * 0000800000007 * ,










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8 9701/35/O/N/25 © UCLES 2025 (ii) Use your observations in (a)(i) to complete Table 3.1 to show whether each species is present in FA 5. Use a tick (✓) if the species is present. Use a cross (✗) if the species is not present. Table 3.1 Zn2+ SO4 2– H2O [1] (b) You are provided with solid FA 6. (i) Heat a few crystals of FA 6 in a hard-glass test-tube until no further gas is evolved. Record all your observations. Leave the test-tube until it is cool. Keep the cooled residue for use in (b)(ii). … … … [2] (ii) To the cooled residue from (b)(i), add approximately 3 cm depth of distilled water and stir. Filter the solution formed into a test-tube. The colour of the solution is … . [1] * 0000800000008 * ,










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9 9701/35/O/N/25 © UCLES 2025 (c) You are provided with aqueous solutions FA 7 and FA 8 and with solid FA 9. FA 7 is an aqueous solution of FA 6. FA 7, FA 8 and FA 9 contain compounds which all have one metal that is the same but which may be in different oxidation states. (i) Carry out the following tests on FA 7, FA 8 and FA 9 and record your observations in Table 3.2. For each test use a 1 cm depth of a solution or a spatula measure of solid. Table 3.2 test observations FA 7 FA 8 FA 9 Test 1 Add hydrogen peroxide. Test 2 Add aqueous sodium hydroxide, then leave to stand. Test 3 Add aqueous iron(II) sulfate. [4] (ii) Suggest the identity of the metal in FA 6 / FA 7, FA 8 and FA 9. The metal is … . [1] (iii) Complete Table 3.3 to suggest the oxidation state of the metal in FA 6 / FA 7 and FA 8. Table 3.3 FA 6 / FA 7 FA 8 oxidation state [1] [Total: 15] * 0000800000009 * ,










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10 9701/35/O/N/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+ * 0000800000010 * ,










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11 9701/35/O/N/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) * 0000800000011 * ,









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12 9701/35/O/N/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. * 0000800000012 * ,









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This document consists of 13 printed pages. © Cambridge University Press & Assessment 2025 [Turn over Cambridge International AS & A Level CHEMISTRY 9701/35 Paper 3 Advanced Practical Skills 1 October/November 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 October/November 2025 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 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 alon gside 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.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 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 thre sholds 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 fro m 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.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 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.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 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 standard isation 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 Rounding error Repeat error or / Blank page or part of script seen

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 6 of 13 Annotation Meaning Error in number of significant figures Transcription error

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 7 of 13 Question Answer Marks 1(a) I 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. Examiner selects 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 titre value Calculate the supervisor’s mean titre 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  ⩽ 0.50 cm3 VI Award if  ⩽ 0.30 cm3 VII Award if  ⩽ 0.20 cm3 3

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 8 of 13 Question Answer Marks 1(b) Correctly calculates mean titre to 2 dp • 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 dp and be rounded to nearest 0.01 cm3. (e.g. 26.675 cm3 must be rounded to 26.68 cm3) 1 1(c)(i) All answers to (c)(ii), (c)(iii) and (c)(iv) to 3 − 4 sf 1 1(c)(ii) Correctly calculates amount of manganate(VII) = 0.02  volume in (b) / 1000 mol 1 1(c)(iii) Correctly uses M1 Amount of ethanedioic acid = (c)(ii)  5 / 2 mol M2 Concentration of FA 1 = (c)(ii)  5 / 2  1000 / 25 mol dm−3 2 1(c)(iv) Correctly uses Mr = 6.2(0) / (c)(iii) 1 1(c)(v) (Mr − 90) / 18 AND correctly calculates answer as integer 1 1(d) H+ needed in the reaction / H+ used in / appears in the equation 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 9 of 13 Question Answer Marks 2(a) l Six correct headings with units in results space • (Mass) crucible + lid / g • (Mass) crucible + lid + FA 4 / g • (Mass) crucible + lid + residue / contents after first heating / g • (Mass) crucible + lid + residue after second heating / g • (Mass) FA 4 (used) / g • (Mass) residue / g Display of units: / g, (g), in g, in gram(me)s or in (column) heading covering all entries 1 ll Four readings in space provided • All four weighings recorded to same decimal places (either to two or to three) • Reading after 2nd heating within + 0.02 and − 0.05 of reading after 1st heating 1 ll Correct subtractions • Correct calculations of mass FA 4 and residue AND • Mass of FA 4 is between 2.90 and 3.40 g. 1 lV and V Accuracy Theoretical value = 1.78 Calculate and record candidate’s mass ratio = mass FA 4 / mass of residue. Award IV if 1.51 ⩽ candidate’s mass ratio ⩽ 2.05 Award V if 1.60 ⩽ candidates mass ratio ⩽ 1.96 2

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 10 of 13 Question Answer Marks 2(b)(i) Correctly uses M1 Amount ZnSO4 = mass residue / 161.5 mol AND answer given to 2 – 4 sf Correctly calculates M2 Amount H2O = mass water lost / 18 mol AND answer given to 2–4 sf 2 2(b)(ii) M1 y = moles H2O / moles ZnSO4 M2 Expression evaluated and y correctly calculated quoted as integer 2 2(c) The (anhydrous ethanedioic) acid would decompose (on heating) / is flammable 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 11 of 13 Question Answer Marks FA 5 is MgSO4•7H2O; FA 6 is KMnO4; FA 7 is acidified KMnO4(aq); FA 8 is MnSO4 or MnCl2; FA 9 is MnO2 3(a)(i) M1 Heat (solid FA 5) AND observe condensation, droplets, steam, water vapour M2 Make an aqueous solution of FA 5 / dissolve in water to use for tests M3 (To portion of the solution) add aqueous NH3 AND white ppt AND insoluble in excess NH3 M4 (To portion of the solution) add aqueous barium chloride or barium nitrate AND white precipitate M5 to distinguish sulfate / sulfite (white precipitate from M4) insoluble in hydrochloric OR nitric acid OR KMnO4 is not decolourised / remains purple (added after M4 or directly to FA 5 (aq)) 5 3(a)(ii) Zn2+ X SO42− ✓ H2O ✓ 1 3(b)(i) • (FA 6) starting colour purple • solid jumps / moves around • black residue • test with glowing splint • splint relights / glows more brightly 2 3(b)(ii) (dark) Green 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 12 of 13 Question Answer Marks 3(c)(i) 'No change' 2 correct = *, 3 correct = ** 2* = 1 mark Max mark = 4 test observations FA 7 FA 8 FA 9 Test 1 Add hydrogen peroxide Bubbles/ effervescence * Purple / FA 7 (solution) to colourless (solution) * (Gas / oxygen) relights glowing splint * No change Bubbles / effervescence * (Gas/ oxygen) relights glowing splint * Test 2 Add sodium hydroxide, then Off-white ppt* No change leave to stand brown ppt on standing* Test 3 Add aqueous iron(ll) sulfate Turns colourless / yellow OR colourless / yellow solution formed* No change 4 3(c)(ii) manganese / Mn 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 13 of 13 Question Answer Marks 3(c)(iii) FA 6 / FA 7 FA 8 oxidation state (+)7 (+)2 1