Cambridge A Level Chemistry 9701 — 2022 May/June Paper 3 · Variant 5

*6297166006* CHEMISTRY 9701/35 Paper 3 Advanced Practical Skills 1 May/June 2022  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. IB22 06_9701_35/5RP © UCLES 2022 [Turn over This document has 12 pages. Cambridge International AS & A Level Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/35/M/J/22 © UCLES 2022 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 final answer to each step of your calculations. 1 Basic copper(II) carbonate contains both copper(II) carbonate, CuCO3, and copper(II) hydroxide, Cu(OH)2. The ratio of these two components can be different in samples from different sources. This means that the formula of basic copper(II) carbonate can be written as CuCO3•xCu(OH)2. Both the carbonate and the hydroxide react with acids. CuCO3(s) + 2HCl (aq) → CuCl 2(aq) + CO2(g) + H2O(l) Cu(OH)2(s) + 2HCl (aq) → CuCl 2(aq) + 2H2O(l) You will determine the value of x in a sample of basic copper(II) carbonate by reacting it with excess acid and measuring the mass of carbon dioxide given off. FA 1 is basic copper(II) carbonate, CuCO3•xCu(OH)2. FA 2 is 2.0 mol dm–3 hydrochloric acid, HCl. (a) Method ● Use the 25 cm3 measuring cylinder to transfer 25.0 cm3 of FA 2 into a conical flask. ● Weigh the flask with the acid. Record the mass. ● Weigh the container with FA 1. Record the mass. ● Carefully tip all of FA 1 into the acid in the conical flask. Swirl the contents of the flask and leave the flask to stand. ● Weigh the container with any residual FA 1. Record the mass. ● Calculate and record the mass of FA 1 added to the flask. ● Calculate and record the theoretical initial mass of flask + acid + FA 1. ● Swirl the flask occasionally. Weigh the flask and contents after approximately 5 minutes. Record the mass. During this step you may wish to continue with Question 2 or Question 3. ● Calculate and record the mass of carbon dioxide given off during the experiment. Results  [4] I II III IV

3 9701/35/M/J/22 © UCLES 2022 [Turn over (b) Calculations (i) Calculate the amount, in mol, of carbon dioxide given off in the reaction.  amount of CO2 = … mol [1] (ii) Calculate the amount, in mol, of copper(II) carbonate in the sample of FA 1 that you added to the flask.  amount of CuCO3 = … mol Hence calculate the mass of copper(II) carbonate in the sample of FA 1 that you added to the flask.  mass of CuCO3 = … g  [1] (iii) Calculate the mass of copper(II) hydroxide in the sample of FA 1 that you added to the flask.  mass of Cu(OH)2 = … g [1] (iv) Calculate the amount, in mol, of copper(II) hydroxide in the sample of FA 1 that you added to the flask.  amount of Cu(OH)2 = … mol Hence calculate the value of x in the formula of basic copper(II) carbonate, CuCO3•xCu(OH)2.  x = …  [1] (c) In this determination you assume that hydrochloric acid is in excess. Show, by calculation, that this assumption is correct.  [2]  [Total: 10]

4 9701/35/M/J/22 © UCLES 2022 2 In Question 1 you found the value of x in the formula of basic copper(II) carbonate, CuCO3•xCu(OH)2. You will now use another method to find the value of x. Copper(II) ions oxidise iodide ions to produce iodine. 2Cu2+(aq) + 4I–(aq) → I2(aq) + 2CuI(s) The amount of iodine produced can be found by titration with aqueous thiosulfate ions, S2O3 2–. 2S2O3 2–(aq) + I2(aq) → S4O6 2–(aq) + 2I–(aq) FA 3 contains Cu2+(aq). It was made by reacting 10.40 g of CuCO3•xCu(OH)2 with excess dilute sulfuric acid and making the solution up to 1.00 dm3 with distilled water. FA 4 is 0.100 mol dm–3 sodium thiosulfate, Na2S2O3. FA 5 is aqueous potassium iodide, KI. FA 6 is starch indicator. (a) Method ● Fill the burette with FA 4. ● Pipette 25.0 cm3 of FA 3 into a conical flask. ● Rinse the 25 cm3 measuring cylinder with approximately 5 cm3 of FA 5. Discard the solution used for rinsing. ● Use the 25 cm3 measuring cylinder to add 15 cm3 of FA 5, an excess of KI, to the conical flask. The solution will turn brown because iodine is formed. ● Add FA 4 from the burette until the mixture changes to pale brown. ● Add approximately 10 drops of FA 6. The mixture will turn blue-black. ● Continue adding FA 4 from the burette until the blue-black colour disappears to leave an off-white solid. This is the end-point of the titration. ● Carry out 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 certain any recorded results show the precision of your practical work. ● Record in a suitable form below, all your burette readings and the volume of FA 4 added in each accurate titration.  [7] I II III IV V VI VII

5 9701/35/M/J/22 © UCLES 2022 [Turn over (b) From your accurate titration results, calculate a suitable mean value to be used in your calculations. Show clearly how you have obtained the mean value.  25.0 cm3 of FA 3 required … cm3 of FA 4. [1] (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 thiosulfate ions present in the volume of FA 4 you have calculated in (b).  amount of S2O3 2– = … mol [1] (iii) Use your answer to (c)(ii), and the equations for the reactions involved, to calculate the amount, in mol, of copper(II) ions present in 25.0 cm3 of FA 3.  amount of Cu2+ in 25.0 cm3 = … mol Hence deduce the amount, in mol, of copper(II) ions present in 1.00 dm3 of FA 3.  amount of Cu2+ in 1.00 dm3 = … mol  [1] (iv) Use your answer to (c)(iii) to calculate the mass of copper(II) ions in 1.00 dm3 of FA 3.  mass of Cu2+ in 1.00 dm3 = … g [1]

6 9701/35/M/J/22 © UCLES 2022 (v) The formula of basic copper(II) carbonate is CuCO3•xCu(OH)2. Write an expression, including x, for the mass of Cu2+ ions in one mole of CuCO3•xCu(OH)2.  mass of Cu2+ ions in one mole of CuCO3•xCu(OH)2 = … g [1] (vi) The formula of basic copper(II) carbonate is CuCO3•xCu(OH)2. Write an expression, including x, for the mass of one mole of CuCO3•xCu(OH)2.  mass of one mole of CuCO3•xCu(OH)2 = … g [1] (vii) The expression below links the masses of copper(II) ions in FA 3 and in one mole. mass of Cu2+ present in sample of FA 3 = mass of Cu2+ in one mole of CuCO3•xCu(OH)2 mass of CuCO3•xCu(OH)2 used mass of one mole of CuCO3•xCu(OH)2 Using this expression, show how you could determine the value of x in the formula of basic copper(II) carbonate, CuCO3•xCu(OH)2.  [3]  [Total: 17]

7 9701/35/M/J/22 © UCLES 2022 [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. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests should be attempted. 3 (a) FA 7 is a sample of basic copper(II) carbonate. Place a small spatula measure of FA 7 into a hard-glass test-tube and heat the tube, gently at first and then more strongly. Record all your observations. … … … … [2]

8 9701/35/M/J/22 © UCLES 2022 (b) FA 8 is an aqueous solution containing Cu2+ ions. (i) Carry out the following tests using a 1 cm depth of FA 8 in a test-tube for each test. Record your observations. Table 3.1 test observations Test 1 Add a 1 cm depth of aqueous EDTA. Test 2 Add concentrated hydrochloric acid (CARE, corrosive) dropwise until no further change is seen. Test 3 Add a small spatula measure of metal M. Leave the test-tube to stand.  [2] (ii) Suggest a possible ionic equation for the reaction between M and FA 8 in Test 3. Include state symbols. … [1] (c) Carry out tests to identify M. Use only a small spatula measure of M. Do not use concentrated hydrochloric acid in your tests. (i) Record the tests you carry out and the observations you make, in a table, in the space below.  [3] (ii) From your observations in (c)(i), identify M.  M is … . [1]

9 9701/35/M/J/22 © UCLES 2022 [Turn over (d) FA 9 and FA 10 are sodium compounds that contain either a halide or a carbonate. Carry out tests to confirm the identity of FA 9 and FA 10. Record the tests you carry out, the observations you make and your conclusions in a table in the space below.  [4]  [Total: 13]

10 9701/35/M/J/22 © UCLES 2022 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+

11 9701/35/M/J/22 © UCLES 2022 3 Tests for gases gas test and test result ammonia, NH3 turns damp red litmus paper blue carbon dioxide, CO2 gives a white ppt. with limewater hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint 4 Tests for elements element test and test result iodine, I2 gives blue-black colour on addition of starch solution Important values, constants and standards molar gas constant R = 8.31 J K–1 mol–1 Faraday constant F = 9.65 × 104 C mol–1 Avogadro constant L = 6.022 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 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)

12 9701/35/M/J/22 © UCLES 2022 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. 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 144.4 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 –

This document consists of 10 printed pages. © UCLES 2022 [Turn over Cambridge International AS & A Level CHEMISTRY 9701/35 Paper 3 Advanced Practical Skills 1 May/June 2022 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 2022 series for most Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 2 of 10 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors 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 May/June 2022 © UCLES 2022 Page 3 of 10 GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind. Science-Specific Marking Principles 1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks should not be awarded if the keywords are used incorrectly. 2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored. 3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection). 4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where necessary and any exceptions to this general principle will be noted. 5 ‘List rule’ guidance For questions that require n responses (e.g. State two reasons …):  The response should be read as continuous prose, even when numbered answer spaces are provided.  Any response marked ignore in the mark scheme should not count towards n.  Incorrect responses should not be awarded credit but will still count towards n.  Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should be treated as a single incorrect response.  Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 4 of 10 6 Calculation specific guidance Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show your working’. For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values. For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1 and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme. Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded. Exceptions to this general principle will be noted in the mark scheme. 7 Guidance for chemical equations Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme. State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 5 of 10 Question Answer Marks 1(a) l Unambiguous headings and correct units Units: / g, (g), in gram(me)s with each entry or in heading.  (mass of) flask + acid  (mass of) container + FA 1  (mass of) container (+ residue)  (final / constant mass of) flask + contents  (mass of) FA 1 (added)  theoretical (initial / total) mass  (mass of) CO2 (evolved) ll Four weighings recorded to the same number of decimal places and to at least 2 dp lll Three masses correctly calculated IV Award if ratio 2 mass mass CO FA 1 (to 2 dp) is within 20% of supervisor’s value 4 1(b)(i) Correctly calculates moles of CO2 = mass loss / 44 AND answer to 2–4 significant figures 1 1(b)(ii) Deduces moles CuCO3 = (b)(i) AND correctly uses mass CuCO3 = moles  123.5 AND answer to 2–4 significant figures 1 1(b)(iii) Mass Cu(OH)2 = FA 1 – (ii) 1 1(b)(iv) Moles Cu(OH)2 = (iii) / 97.5 AND ratio moles Cu(OH)2/ moles CuCO3 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 6 of 10 Question Answer Marks 1(c) M1 moles HCl = 2  25 / 1000 = 0.05 AND moles reacting in FA 1 = moles CuCO3 + moles Cu(OH)2 M2 0.05 > 2  (moles CuCO3 + moles Cu(OH)2) OR M1 moles of HCl required = 2  (moles CuCO3 + moles Cu(OH)2) M2 vol of HCl required = moles required  1000 / 2 AND volume required < 25 cm3 2

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 7 of 10 Question Answer Marks 2(a) I Initial and final readings AND titre recorded for rough titre and accurate titre details tabulated ll Headings and units correct for accurate titrations .  initial / final (burette) reading / volume or reading / volume at start / finish  titre or volume / FA 4  added / used Units:(cm3) or / cm3 or in cm3 or cm3 by every entry IIl All accurate burette readings are recorded to the nearest 0.05 cm3 IV Final (uncorrected) titre is within 0.10 cm3 of any other accurate titre For assessment of accuracy the examiner should round any burette readings to the nearest 0.05 cm3, check subtractions and then select the ‘best titres’ using the hierarchy: two (or more) accurate identical titres, then two (or more) accurate titres within 0.05 cm3., then two (or more) accurate titres within 0.10 cm3 etc. These best titres should be used to calculate the mean corrected titre to the nearest 0.01 cm3. Award V if  ⩽ 0.80 cm3 Award VI if ⩽ 0.50 cm3 Award VII if ⩽ 0.30 cm3 If supervisor’s titre is ⩽ 10.00 cm3 then tolerances are 0.15, 0.25 and 0.40 cm3. If supervisor’s titre is ⩽ 5.00 cm3 then tolerances are 0.10, 0.15 and 0.25 cm3. 7 2(b) Candidate must average two (or more) accurate titres where the total spread is ≤ 0.20 cm3. Working must be shown or ticks must be put next to the two (or more) accurate titres selected. 1 2(c)(i) All quoted answers to (c)(ii) to (c)(iv) to 3–4 significant figures (minimum 3 answers attempted). 1 2(c)(ii) Correctly calculates moles in (b)  0.1 / 1000 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 8 of 10 Question Answer Marks 2(c)(iii) Correctly uses moles Cu2+ in 25 cm3 = (c)(ii) AND moles Cu2+ in 1.0 dm3 = moles Cu2+ in 25 cm3  40 1 2(c)(iv) Correctly uses (c)(iii)  63.5 1 2(c)(v) Correct expression mass of Cu2+ = 63.5 (1 + x) 1 2(c)(vi) mass of 1 mol = 123.5 + 97.5x 1 2(c)(vii) M1 LHS 10.4g (c)(iv) M2 RHS 63.5 (1 ) 123.5 97.5   x x M3 shows cross multiplication and simplification in attempt to calculate x 3

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 9 of 10 Question Answer Marks FA 7 is CuCO3•Cu(OH)2(s); FA 8 is CuSO4(aq); M is Mg(s); FA 9 is Na2CO3(aq); FA 10 is KI(aq) 3(a) Any two from:  solid goes black / colour change green to black  condensation / water on cool part tube / steam  gas / CO2 given off turns limewater to white ppt 2 3(b)(i) test observation + edta darker blue * + HCl green / yellow * + M solution goes pale * black solid / ppt * ignore any fizz 2 * = 1 mark 2 3(b)(ii) Cu2+(aq) + M(s) → Cu(s) + M2+(aq) OR Cu2+(aq) + 2M(s) → Cu(s) + 2M+(aq) OR 3Cu2+(aq) + 2M(s) → 3Cu(s) + 2M3+(aq) 1 3(c)(i) M1 add named acid AND effervescence M2 (to resulting solution) add NaOH AND NH3 M3 white ppt insoluble in excess for both alkalis 3 3(c)(ii) M is magnesium 1

9701/35 Cambridge International AS & A Level – Mark Scheme PUBLISHED May/June 2022 © UCLES 2022 Page 10 of 10 Question Answer Marks 3(d) M1 table with unambiguous headings (test/reagent and observations / results and conclusion) AND any 2 or more reagents M2 selects suitable reagents AgNO3(aq) AND either named (dilute) acid or named solution that will form a ppt with carbonate but not with a halide e.g. named (aq) barium salt M3 result and conclusion for FA 9 fizz / effervescence / bubbling with acid / correct colour of ppt with suitable salt solution AND FA 9 is carbonate / CO32− M4 result and conclusion for FA 10 yellow ppt (ignore addition of (aq) ammonia) AND FA 10 is iodide / I− 4