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Chemistry 9701/32 May/June 2019: question paper and mark scheme

Cambridge AS & A Level Chemistry (9701), Paper 3 Advanced Practical Skills 2, May/June 2019. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.

9701_s19_qp_329701_s19_ms_329701/32/M/J/19

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Paper
Paper 3 Advanced Practical Skills 2
Total marks
40
Questions
3
Code on the paper
9701/32/M/J/19
9701_s19_ms_32.pdf

9701/32 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 116 marks

Question

Amidosulfonic acid is a monoprotic acid with the formula HSOxNH2. In this experiment you will determine the value of x in the formula by titration with an alkali. FB 1 is amidosulfonic acid, HSOxNH2. You are supplied with approximately 3.0 g. FB 2 is 0.110 mol dm–3 sodium hydroxide, NaOH. thymolphthalein indicator (a) Method Preparing a solution of amidosulfonic acid ●● Weigh the empty beaker. Record the mass. ●● Add 2.50 –2.70 g of FB 1 to the beaker. Weigh the beaker and its contents. Record the mass. ●● Calculate and record the mass of FB 1 used. ●● Add approximately 100 cm3 of distilled water to the beaker and stir to dissolve FB 1. ●● Transfer the solution to the 250 cm3 volumetric flask. ●● Rinse the beaker twice with approximately 20 cm3 of distilled water each time and add to the volumetric flask. ●● Add distilled water to the volumetric flask to make 250 cm3 of solution. ●● Shake the volumetric flask to mix the solution thoroughly and label it FB 3. Titration of FB 3 ●● Fill the burette with FB 2. ●● ipette 25.0 cm3 of FB 3 into a conical flask. P ●● Add a few drops of thymolphthalein to the conical flask. ●● Carry out a rough titration. ●● Record your burette readings and the rough titre 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 any recorded results show the precision of your practical work. ●● Record all of your burette readings and the volume of FB 2 added in each accurate titration. I II III IV V VI VII [8] VIII (b) From your accurate titration results, obtain a suitable value for the volume of FB 2 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FB 3 required …… cm3 of FB 2. [1] (c) Calculations (i) Give your answers to (ii), (iii), (iv) and (v) to the appropriate number of significant figures. [1] (ii) Calculate the number of moles of sodium hydroxide, NaOH, in the volume of FB 2 calculated in (b). moles of NaOH = …… mol [1] (iii) One mole of sodium hydroxide neutralises one mole of amidosulfonic acid. Complete the equation for the reaction of amidosulfonic acid with sodium hydroxide. Include state symbols. ……NaOH…… + ……HSOxNH2…… …… + …… State the number of moles of amidosulfonic acid that reacted with the number of moles of NaOH calculated in (ii). moles of HSOxNH2 = …… mol [1] (iv) Use your results on page 2 and your answer to (iii) to calculate the relative formula mass, Mr, of amidosulfonic acid. Mr of amidosulfonic acid = …… [1] (v) Calculate the value of x in the formula of amidosulfonic acid, HSOxNH2. x = …… [1] (d) The salts produced from amidosulfonic acid are called amidosulfonates. You are to carry out an experiment using FB 1 to find out if barium amidosulfonate is soluble in water. ●● Describe your experiment. ●● Record your observation(s) and conclusion. . …… . …… . …… . …… . …… [2] [Total: 16] Question 2 starts on the next page.

Mark scheme

1(a) I: All the following data is recorded, with ‘g’ units 1 • three masses with unambiguous headings (not ‘weight’) • both weighings recorded to same number of d.p. (one or more) • mass of FB 1 is correctly subtracted • mass of FB 1 used is between 2.5 and 2.7 g II: All the following data is recorded 1 • rough titration: both burette readings and the rough titre • initial and final burette readings for two (or more) accurate titrations (i.e. a 2 × 2 ‘box’) Headings and units are not required for this mark III: Correct headings and units given in the accurate titration table 1 • initial / start and (burette) reading / volume • final / end and (burette) reading / volume • titre or volume / FB 2 and used / added (not ‘amount’) • unit: / cm3 or (cm3) or in cm3 (for each heading) or cm3 unit given for each volume recorded IV: All accurate burette readings are recorded to the nearest 0.05 cm3. 1 V: The final accurate titre recorded is within 0.10 cm3 of any other accurate titre 1 Award VI, VII and VIII if δ ≤ 0.10 (cm3 g–1) 1 Award VI and VII if 0.10 < δ ≤ 0.20 1 Award VI, only if 0.20 < δ ≤ 0.40 1 1(b) Candidate calculates the mean correctly. 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. • the mean should be quoted to 2 d.p., and be rounded to nearest 0.01 cm3. 1(c)(i) Significant figures 1 The answers to (ii), (iii) and (iv) must all be expressed to 3 or 4 sig. fig. 1(c)(ii) Correctly calculates no of moles NaOH 1 No. of moles of NaOH used = 0.110 × mean titre / 1000 1(c)(iii) Equation balanced with state symbols correct. 1 NaOH(aq) + HSOxNH2(aq) → NaSOxNH2(aq) + H2O(l) and correct answer: no. of moles of FB 3 = ans (ii) 1(c)(iv) Correct use of 1 M r of FB 1 = mass of FB 1 weighed out / 10 × no of moles of FB 3 (from (iii)) 1(c)(v) Correct expression and gives the answer as an integer 1 x = [ans (iv) – 49.1] / 16 1(d) Method: 1 Dissolve FB 1 in water or use FB 3 and add (aqueous) BaCl 2 / Ba(NO3)2 or (aqueous) barium chloride / barium nitrate Observation: no reaction / no precipitate / solution stays colourless 1 and Deduction: barium amidosulfonate is soluble in water

Question 210 marks

Question

When hydrated copper hydroxycarbonate, CuCO3.Cu(OH)2.yH2O is heated, it decomposes as shown. CuCO3.Cu(OH)2.yH2O(s) 2CuO(s) + CO2(g) + (1 + y)H2O(g) In this experiment, you will heat hydrated copper hydroxycarbonate to decompose it. You will use your results to investigate the value of y. FB 4 is hydrated copper hydroxycarbonate, CuCO3.Cu(OH)2.yH2O. (a) Method ●● Weigh the crucible with its lid and record the mass. ●● Add all the FB 4 from the container into the crucible. ●● Weigh the crucible and lid with FB 4 and record the mass. ●● Place the crucible and contents on the pipe-clay triangle. ●● Heat the crucible and contents gently for approximately two minutes with the lid on. ●● Use tongs to remove the lid and heat strongly for approximately three minutes. ●● Replace the lid and leave the crucible and residue to cool for several minutes. While the crucible is cooling, you may wish to begin work on Question 3. ●● When the crucible is cool, reweigh it with its lid and contents. Record the mass. ●● Calculate and record the mass of FB 4 and the mass of residue obtained. Results I II III IV State the observations made while the decomposition of FB 4 was taking place. . …… . …… [4] (b) Calculations (i) Calculate the number of moles of copper oxide, CuO, obtained as residue. moles of CuO obtained = …… mol [1] (ii) Use your results to calculate the relative formula mass, Mr, of hydrated copper hydroxycarbonate, CuCO3.Cu(OH)2.yH2O. Mr of CuCO3.Cu(OH)2.yH2O = …… [2] (iii) Use the Periodic Table to calculate the relative formula mass of CuCO3.Cu(OH)2. Mr of CuCO3.Cu(OH)2 = …… Use your answer to (ii) and this Mr to comment on the value of y in the formula of hydrated copper hydroxycarbonate. . …… . …… [2] (c) State one way to improve the accuracy of the experiment, using the same mass of FB 4. . …… . …… [1] [Total: 10] Qualitative Analysis Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. At each stage of any test you are to record details of the following: ● colour changes seen; ● the formation of any precipitate and its solubility in an excess of the reagent added; ● the formation of any gas and its identification by a suitable test. You should indicate clearly at what stage in a test a change occurs. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests for ions present should be attempted.

Mark scheme

2(a) I: Table / list of data, to include values and correct headings and units: 1 • Mass of crucible (and lid) • Mass of crucible, (lid) + FB 4 (or ‘contents before heating’) • Mass of crucible, (lid) + residue / CuO / contents after heating • Mass of FB 4 (used) • Mass of residue / CuO (obtained) Accuracy (Q) marks in 2(a) • To assess accuracy, check the masses of FB 4 used and of CuO obtained by the supervisor and by the candidate. • Work out the ratio mass of FB4 / mass of CuO for the supervisor (to 2 d.p.) • Work out ratio (mass FB 4: mass CuO) for the candidate (2 d.p.) • Calculate δ, the difference between these two ratios. Award II and III if δ ⩽ 0.05 1 Award III if 0.05 < δ ⩽ 0.10 1 IV: Observations made during heating 1 (Solid changes from) green / turquoise / cyan / blue-green to black (both colours required) or black solid / residue (formed) 2(b)(i) Correctly calculated no. of moles of CuO 1 • No. of moles CuO = mass of residue / 79.5 • Answer must be correct and expressed to 2, 3 or 4 sig. fig. 2(b)(ii) Correct use of mole ratio 1 : 2 1 • No. of moles of FB 4 = answer (i) / 2 Correctly uses n to calculate Mr of copper hydroxycarbonate, 1 • M r = mass of FB 4 used / no. of moles of FB 4 • Answer (for M r) must be expressed to 2, 3 or 4 sig. fig. • Some working must be shown to access the second mark 2(b)(iii) M r = 221 1 Appropriate comment on the value of y 1 • If answer 2(b)(ii) is less than 221, candidate should state that y is negative, so the experiment has been inaccurate • If answer 2(b)(ii) is between 213 and 229, then (within experimental error) there is no water of crystallisation • If answer 2(b)(ii) is greater than 221, candidate should calculate the value of y and state that it should be an integer 2(c) Heat to constant mass (or description of procedure) 1

Question 314 marks

Question

(a) FB 5 contains one cation and one anion from those listed in the Qualitative Analysis Notes. (i) Transfer a small spatula measure of FB 5 into a hard-glass test-tube. Heat gently at first and then heat strongly, until no further change occurs. Record all your observations. . …… . …… . …… . …… . …… . …… [3] (ii) To a 1 cm depth of dilute hydrochloric acid in a test-tube, add a small spatula measure of FB 5. Record your observations. . …… . …… . …… . …… [2] (iii) Deduce the formula of FB 5. …… [1] (b) FB 6 is a solution of a compound containing one cation from those listed in the Qualitative Analysis Notes. (i) Carry out the following tests using a 1 cm depth of FB 6 in a test-tube for each test. test observations Add two drops of Universal Indicator solution. Add an equal volume of aqueous manganese(II) chloride. Add an equal volume of dilute sulfuric acid. Add a few drops of aqueous silver nitrate, then add aqueous ammonia. Add a few drops of aqueous copper(II) sulfate, then add excess dilute hydrochloric acid. [4] (ii) What can be determined about FB 6 from its reaction with manganese(II) chloride? . …… [1] (iii) Give the ionic equation for the reaction between FB 6 and sulfuric acid. Include state symbols. . …… [1] (iv) When aqueous copper(II) sulfate was added to FB 6, two precipitates were formed. Deduce the identity of the two precipitates. …… and . …… Explain the observation you made when you added excess dilute hydrochloric acid in the final test of (b)(i). . …… . …… . …… [2] [Total: 14] Qualitative Analysis Notes 1 Reactions of aqueous cations reaction with ion NaOH(aq) NH3(aq) aluminium, white ppt. white ppt. Al 3+(aq) soluble in excess insoluble in excess ammonium, no ppt. – NH4+(aq) ammonia produced on heating barium, faint white ppt. is nearly always no ppt. Ba2+(aq) observed unless reagents are pure calcium, white ppt. with high [Ca2+(aq)] no ppt. Ca2+(aq) chromium(III), grey-green ppt. grey-green ppt. Cr3+(aq) soluble in excess insoluble in excess copper(II), pale blue ppt. blue ppt. soluble in excess Cu2+(aq) insoluble in excess giving dark blue solution green ppt. turning brown on contact green ppt. turning brown on contact iron(II), with air with air Fe2+(aq) insoluble in excess insoluble in excess iron(III), red-brown ppt. red-brown ppt. Fe3+(aq) insoluble in excess insoluble in excess magnesium, white ppt. white ppt. Mg2+(aq) insoluble in excess insoluble in excess off-white ppt. rapidly turning brown off-white ppt. rapidly turning brown manganese(II), on contact with air on contact with air Mn2+(aq) insoluble in excess insoluble in excess zinc, white ppt. white ppt. Zn2+(aq) soluble in excess soluble in excess 2 Reactions of anions ion reaction carbonate, CO2 liberated by dilute acids CO3 2– chloride, gives white ppt. with Ag+(aq) (soluble in NH3(aq)) Cl –(aq) bromide, gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)) Br –(aq) iodide, gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)) I –(aq) nitrate, NH3 liberated on heating with OH–(aq) and Al foil NO3–(aq) nitrite, NH3 liberated on heating with OH–(aq) and Al foil NO2–(aq) sulfate, gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids) SO42–(aq) sulfite, gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids) SO3 (aq) 2– 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 (ppt. dissolves with excess CO2) chlorine, Cl 2 bleaches damp litmus paper hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint 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 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 89–103 104 105 106 107 108 109 110 111 112 114 116 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium flerovium livermorium – – – – – – – – – – – – – 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 138.9 140.1 140.9 144.4 – 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) Observations when heating FB 5: 1 • gas / ammonia turns (red) litmus blue Any of the following score one mark each: 2 • condensation produced or water droplets (at top of tube); • white smoke / steam / steamy fumes produced; • solid sublimes / solid forms at the top of the tube; • no residue at the end of the expt. / solid changes to a gas / solid disappears 3(a)(ii) Both observations required for first mark 1 • fizzing / bubbling / effervescence • solid dissolved or colourless solution formed or (reaction is) rapid / vigorous Gas tested: gas / carbon dioxide turns lime water milky / cloudy white / white ppt / chalky 1 3(a)(iii) (NH4)2CO3 1 3(b)(i) Award one mark for every two correct observations (*) 4 test observations + U.I. violet / blue / dark blue / purple * + Mn2+ off-white / pale brown / buff / beige precipitate * turns (darker) brown / dark on standing * + H2SO4 white precipitate * + Ag+ brown / grey precipitate * + NH3 (brown / grey ppt) soluble (in excess) / ppt disappears / forms colourless solution or white ppt forms (on standing) * + Cu2+ (gives a) blue precipitate * + HCl precipitate becomes paler or white / off-white precipitate / solid *

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On this page, free: the mark scheme for AS & A Level Chemistry 9701/32, May/June 2019 (9701_s19_ms_32), and the question paper (9701_s19_qp_32), to read or download, with each question's marking points written out underneath.

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Chemistry 9701/32 for May/June 2019 is out of 40 marks, across 3 questions.

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