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Chemistry 9701/33 May/June 2025: question paper and mark scheme

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

9701_s25_qp_339701_s25_ms_339701/33/M/J/25

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Paper
Paper 3 Advanced Practical Skills 1
Total marks
40
Time
2 hours
Questions
3
Code on the paper
9701/33/M/J/25
9701_s25_ms_33.pdf

9701/33 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 114 marks

Question

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. Results I II III IV V VI VII [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] (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]

Mark scheme

1(a) I All 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. 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 (δ) between the candidate’s mean titre and the supervisor’s mean titre. Award accuracy Q marks as follows: 3 V Award if δ ⩽ 0.80 cm3 VI Award if δ ⩽ 0.50 cm3 VII Award if δ ⩽ 0.30 cm3 1(b) Correct calculation of the mean titre 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 d.p. and be rounded to nearest 0.01 cm3.. 1(c)(i) Significant figures 1 All answers in (c)(ii) – (c)(iv) are expressed to 3 or 4 sf. 1(c)(ii) Correctly calculates 1 amount of MnO4− = ((b) / 1000) × 0.03 mol 1(c)(iii) Correctly uses 1 amount of H2O2 = (c)(ii) × 2.5 mol 1(c)(iv) Correctly uses 1 [H2O2] = (c)(iii) × 40 × 10 mol dm−3 1(d) M1 Student is not correct 2 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.

Question 210 marks

Question

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. 1 H2O2(aq) H2O(l) + 2 O2(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 I II III IV V [5] (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] 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) I Recording of results in the space for results 5 Unambiguous headings AND units for all recorded results: • initial / FA 1 temperature / temp / T; • final / maximum temperature / temp / T • temp(erature) change / rise / ΔT • 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 ΔT: Cand ⩽ 5.0 5.25 – 10.0 10.25 – 15.0 ⩾ 15.25 mean ΔT ΔT1 – ΔT2| ⩽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, δ Sup ⩽ 5.0 5.25 – 10.0 10.25 – 15.0 15.25 – 20.0 20.25 – 25.0 mean ΔT δ ⩽1.0 ⩽1.5 ⩽2.5 ⩽3.5 ⩽4.5 2(b)(i) Correctly calculates 1 Energy change = 40 × 4.18 × ΔT for Exp 2. AND answer given to 2–4 sf. 2(b)(ii) M1 Correctly uses 2 [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(c)(i) Concentration will be lower 1 AND two of: • ΔT / maximum temp will be lower • (calculated / apparent) energy released / change will be lower • amount / moles (of FA 1 / H2O2) will be lower 2(c)(ii) The student is correct 1 AND ΔT 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 ΔT will be lower AND heat loss will be less OR Student is not correct AND ΔT will be lower AND this is cancelled out by a slower reaction. FA 2 is KMnO4(aq); FA 5 is MnO2; FA 6 is FeCl3; FA 7 is KI

Question 316 marks

Question

(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] (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. (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 observations test 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] (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] 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), off-white ppt. rapidly turning brown off-white ppt. rapidly turning brown Mn2+(aq) 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+ 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 F = 9.65 × 104 C mol–1 Faraday constant 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 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 at www.cambridgeinternational.org after the live examination series. 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 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 16 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 filtrate / solution AND (dark) green 2 M2 (green) solution OR turns AND pink / purple 3(a)(ii) M1 filtrate / solution AND yellow / (pale) brown 2 M2 red-brown / brown ppt (with NaOH) AND insoluble in excess 3(a)(iii) oxidising agent / oxidant 1 3(a)(iv) Fe3+(aq) + 3OH−(aq) → Fe(OH)3(s) 1 OR H+ (aq) + OH- (aq) → H2O (l) 3(b)(i) 2 * = 1 mark (round down). 6 FA 6 (FeCl3) FA 7 (KI) Test 1 Red-brown / brown / rust ppt * No change/ no ppt + NaOH (aq) insoluble in excess * AND Heat No change / red litmus does not turn blue No change / red litmus does not turn blue * AND Test 2 No change / purple colour / solution remains * (mixture/solution) turns brown / red-brown * + acidified KMNO4(aq) Test 3 solution turns yellow / red-brown / brown * + FA 1, H2O2, Effervescence / fizzing / bubbling* then (gas / O2) relights a glowing splint* + starch dark blue / blue-black / black * solution Test 4 Effervescence * No change * + Na2CO3(aq) Gas / CO2 / fizz forms white ppt with limewater * Red-brown / orange-brown / brown ppt. * 3(b)(ii) silver nitrate / AgNO3 AND white ppt 1 3(b)(iii) FA 6: Fe3+, H+, Cl– 3 FA 7: I–, unknown 2 or 3 correct = 1 mark 4 correct = 2 marks 5 correct = 3 marks

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Where can I find the 9701/33 May/June 2025 mark scheme?

On this page, free: the mark scheme for AS & A Level Chemistry 9701/33, May/June 2025 (9701_s25_ms_33), and the question paper (9701_s25_qp_33), to read or download, with each question's marking points written out underneath.

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Chemistry 9701/33 for May/June 2025 is out of 40 marks, with 2 hours to answer it, across 3 questions.

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