Free until 14 Nov · 80% off for the first 100 · Pricing

Get started

Chemistry 9701/31 October/November 2025: question paper and mark scheme

Cambridge AS & A Level Chemistry (9701), Paper 3 Advanced Practical Skills 1, October/November 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.

9701_w25_qp_319701_w25_ms_319701/31/O/N/25

Mark my answers with AIRead the paper and scheme
Paper
Paper 3 Advanced Practical Skills 1
Total marks
40
Time
2 hours
Questions
3
Code on the paper
9701/31/O/N/25
9701_w25_ms_31.pdf

9701/31 mark scheme, question by question

Each question as it's printed, and the mark scheme's points for it, as text. Diagrams, tables and graphs are in the PDFs above.

Question 115 marks

Question

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. * 0000800000003 * DFD 3 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 FA 1 required …… cm3 of FA 2. [1] * 0000800000004 * DFD 4 (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] * 0000800000005 * DFD 5

Mark scheme

1(a) I The following data are recorded: 1 • two burette readings AND titre for the rough titration • initial and final burette readings for two (or more) accurate titrations II Titre values recorded for accurate titrations, AND 1 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. 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 (δ) between the candidate’s mean titre and the supervisor’s mean titre Award accuracy Q marks as follows: 3 V Award if δ ⩽ 0.50 cm3 VI Award if δ ⩽ 0.30 cm3 VII Award if δ ⩽ 0.20 cm3 1(b) Correctly calculates mean titre to 2 dp 1 • 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(c)(i) All answers to (c)(ii), (c)(iii) and (c)(iv) to 3 − 4 sf 1 1(c)(ii) Correctly calculates 1 amount of manganate( VII) = 0.02 × volume in (b) / 1000 mol 1(c)(iii) Correctly uses 2 M1 Amount of ethanedioic acid = (c)(ii) × 5 / 2 mol M2 Concentration of FA 1 = (c)(ii) × 5 / 2 × 1000 / 25 mol dm−3 1(c)(iv) Correctly uses 1 Mr = 6.2(0) / (c)(iii) 1(c)(v) (Mr − 90) / 18 1 AND correctly calculates answer as integer 1(d) H+ needed in the reaction / H+ used in / appears in the equation 1

Question 210 marks

Question

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 I II III IV V [5] * 0000800000006 * DFD 6 (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] * 0000800000007 * DFD 7 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.

Mark scheme

2(a) l Six correct headings with units in results space 1 • (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 ll Four readings in space provided 1 • 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 ll Correct subtractions 1 • Correct calculations of mass FA 4 and residue AND • Mass of FA 4 is between 2.90 and 3.40 g. lV and V Accuracy 2 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(b)(i) Correctly uses 2 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(b)(ii) M1 y = moles H2O / moles ZnSO4 2 M2 Expression evaluated and y correctly calculated quoted as integer 2(c) The (anhydrous ethanedioic) acid would decompose (on heating) / is flammable 1 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

Question 315 marks

Question

(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] * 0000800000008 * DFD 8 (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+ SO42– H 2O [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] * 0000800000009 * DFD 9 (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] * 0000800000010 * DFD 10 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 no ppt. [Ba2+(aq)] is very low calcium, Ca2+(aq) white ppt. unless [Ca2+(aq)] is very no ppt. low chromium(III), Cr3+(aq) grey-green ppt. soluble in excess grey-green ppt. insoluble in excess giving dark green solution 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 green ppt. turning brown on contact with air contact with air insoluble in excess 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 off-white ppt. rapidly turning brown on contact with air on contact with air insoluble in excess insoluble in excess zinc, Zn2+(aq) white ppt. soluble in excess white ppt. soluble in excess 2 Reactions of anions anion reaction carbonate, CO32– 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, SO42–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids); gives white ppt. with high [Ca2+(aq)] sulfite, SO32–(aq) gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids); decolourises acidified aqueous KMnO4 thiosulfate, S2O32–(aq) gives off-white / pale yellow ppt. slowly with H+ * 0000800000011 * DFD 11 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) The Periodic Table of Elements Group 1 2 13 14 15 16 17 18 1 2 H He hydrogen helium Key 1.0 4.0 3 4 atomic number 5 6 7 8 9 10 Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon 6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon DFD 23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 at www.cambridgeinternational.org after the live examination series. K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton 39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 12 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon 85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 lanthanoids Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon 132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – – 87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson – – – – – – – – – – – – – – – – – 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium 138.9 140.1 140.9 144.2 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium – 232.0 231.0 238.0 – – – – – – – – – – – Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge

Mark scheme

3(a)(i) M1 Heat (solid FA 5) 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 NH 3 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)) 3(a)(ii) 1 Zn2+ X SO42− ✓ H2O ✓ 3(b)(i) • (FA 6) starting colour purple 2 • solid jumps / moves around • black residue • test with glowing splint • splint relights / glows more brightly 3(b)(ii) (dark) Green 1 3(c)(i) 'No change' 2 correct = *, 3 correct = ** 4 2* = 1 mark Max mark = 4 test observations FA 7 FA 8 FA 9 Test 1 Bubbles/ effervescence * No change Bubbles / effervescence * Add hydrogen peroxide Purple / FA 7 (solution) to (Gas/ oxygen) relights colourless (solution) * glowing splint * (Gas / oxygen) relights glowing splint * Test 2 Off-white ppt* No change Add sodium hydroxide, then leave to stand brown ppt on standing* Test 3 Turns colourless / yellow No change Add aqueous OR colourless / yellow iron(ll) sulfate solution formed* 3(c)(ii) manganese / Mn 1 3(c)(iii) 1 FA 6 / FA 7 FA 8 oxidation (+)7 (+)2 state

Checked your answers against these? Let AI mark the whole paper, on your own working.

Mark my 9701/31

How this paper is marked

Examiners follow the generic marking principles at the front of the scheme, then each question's points: method (M), accuracy (A) and independent (B) marks, error carried forward where the scheme allows it, and positive marking, so you're credited for what you got right.

Check your answers against it

Done this paper? Upload your script and CIE Buddy's AI marker marks it question by question against this exact scheme, puts the ticks on your own working and says what each lost mark needed.

Other variants, October/November 2025

9701/31 in other series

Find another Chemistry paper

Every AS & A Level Chemistry mark scheme

Question papers and mark schemes © Cambridge University Press & Assessment. CIE Buddy is independent and not connected to Cambridge.

9701/31 questions

Where can I find the 9701/31 October/November 2025 mark scheme?

On this page, free: the mark scheme for AS & A Level Chemistry 9701/31, October/November 2025 (9701_w25_ms_31), and the question paper (9701_w25_qp_31), to read or download, with each question's marking points written out underneath.

How many marks is 9701/31 out of?

Chemistry 9701/31 for October/November 2025 is out of 40 marks, with 2 hours to answer it, across 3 questions.

Can I get my 9701/31 answers marked?

Yes. Upload your answers to 9701/31/O/N/25 as a PDF or photos, and CIE Buddy marks every question against this paper's official mark scheme, using Cambridge's marking rules. You get your score, each lost mark explained on your own script, and the topics to revise. It's a guide, not an official Cambridge grade.