Cambridge A Level Chemistry 9701 — 2016 Feb/March Paper 3 · Variant 3

READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Give details of the practical session and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 10 and 11. A copy of the Periodic Table is printed on page 12. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. CHEMISTRY 9701/33 Paper 3 Advanced Practical Skills 1 February/March 2016 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level This document consists of 12 printed pages. [Turn over IB16 03_9701_33/4RP © UCLES 2016 *9942765474* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/33/F/M/16 © UCLES 2016 1 You will determine the enthalpy change, ∆H, of the reaction between magnesium and hydrochloric acid. To do this you will measure the change in temperature when a piece of magnesium ribbon reacts with an excess of hydrochloric acid. Mg(s) + 2HCl (aq) → MgCl 2(aq) + H2(g) FA 1 is hydrochloric acid, HCl. FA 2 is magnesium ribbon, Mg. (a) Method • Weigh the FA 2 and record the mass in the space below. • Support the plastic cup in the 250 cm3 beaker. • Coil the FA 2 so that it will fit into the bottom of the plastic cup then remove it. • Use the measuring cylinder to transfer 25 cm3 of FA 1 into the plastic cup. • Place the thermometer in the acid and tilt the cup if necessary so that the bulb of the thermometer is fully covered. Record the temperature at time = 0 in the table of results. • Start timing and do not stop the clock until the whole experiment has been completed at time = 8 minutes. • Record the temperature of the acid every half minute for 2 minutes. • At time = 2 2 1 minutes carefully drop the coil of FA 2 into the acid and stir the mixture. • Record the temperature of the mixture at time = 3 minutes and complete the table by recording the temperature every half minute. Stir the mixture between thermometer readings. Results mass of FA 2 = … g time / minutes 0 2 1 1 1 2 1 2 2 2 1 3 3 2 1 4 temperature / °C time / minutes 4 2 1 5 5 2 1 6 6 2 1 7 7 2 1 8 temperature / °C [4] I II III IV

3 9701/33/F/M/16 © UCLES 2016 [Turn over (b) Plot a graph of temperature on the y-axis against time on the x-axis on the grid below. The scale for the temperature axis should extend 10 °C greater than the maximum temperature you recorded. You will use the graph to determine the theoretical maximum temperature rise at 2 2 1 minutes. Draw two lines of best fit through the points on your graph, the first for the temperature before adding FA 2 and the second for the cooling of the mixture once the reaction is complete. Extrapolate the two lines to 2 2 1 minutes, draw a vertical line between the two and determine the theoretical rise in temperature at this time. theoretical rise in temperature at 2 2 1 minutes = … °C [4] I II III IV

4 9701/33/F/M/16 © UCLES 2016 (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Use your answer to (b) to calculate the heat energy, in joules, given out when FA 2 is added to FA 1. (Assume 4.2 J of heat energy raises the temperature of 1.0 cm3 of the mixture by 1.0 °C.) heat energy evolved = … J (ii) Use the Periodic Table on page 12 and your answer to (i) to calculate the enthalpy change, in kJ mol–1, when 1 mole of magnesium, FA 2, reacts with hydrochloric acid, FA 1. enthalpy change = … … kJ mol–1 (sign) (value) [3] (d) A student carried out the same procedure using the same concentration of sulfuric acid, H2SO4, instead of hydrochloric acid. Before starting the experiment the student predicted that the enthalpy change would be twice that with hydrochloric acid. Was the student correct? Explain your answer. … … [1] (e) The enthalpy change determined in (c)(ii) is only an approximation of the actual value. Suggest and explain one improvement you would make to the method in (a) to increase the accuracy of the experiment. … … [1] [Total: 13]

5 9701/33/F/M/16 © UCLES 2016 [Turn over 2 You will determine the concentration of the hydrochloric acid used in Question 1 by titration of a diluted solution of FA 1 with aqueous sodium hydroxide of known concentration. NaOH(aq) + HCl (aq) → NaCl (aq) + H2O(l) FA 3 is a diluted solution of FA 1, hydrochloric acid, HCl. FA 3 was prepared by running 25.00 cm3 of FA 1 into a volumetric flask and adding distilled water until the total volume was 250.0 cm3. FA 4 is 0.100 mol dm–3 sodium hydroxide, NaOH. bromophenol blue indicator (a) Method • Fill the burette with FA 4. • Pipette 25.0 cm3 of FA 3 into a conical flask. • Add about 10 drops of bromophenol blue. • Perform a rough titration and record your burette readings in the space below. The end point is reached when the solution becomes a permanent blue-violet colour. 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 of your burette readings and the volume of FA 4 added in each accurate titration. [7] (b) From your accurate titration results, obtain a suitable value to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FA 3 required … cm3 of FA 4. [1] I II III IV V VI VII

6 9701/33/F/M/16 © UCLES 2016 (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of sodium hydroxide present in the volume of FA 4 recorded in (b). moles of NaOH = … mol (ii) Use your answer to (i) and the equation on page 5 to determine the number of moles of hydrochloric acid present in 25.0 cm3 of FA 3. moles of HCl = … mol (iii) Use your answer to (ii), and any relevant information given on page 5, to calculate the concentration, in mol dm–3, of hydrochloric acid in FA 1. concentration of HCl in FA 1 = … mol dm–3 (iv) Show, by calculation, that the hydrochloric acid in Question 1 was in excess. [5] (d) The error in the volume reading of a pipette is ±0.06 cm3 which gives a maximum percentage error of 0.24% for 25.0 cm3 of FA 3. The error in a single burette reading is ±0.05 cm3. Calculate the maximum percentage error in the volume of FA 4 used in (b) and deduce which solution, FA 3 or FA 4, was measured more accurately. maximum percentage error for volume of FA 4 in (b) = … % … was measured more accurately. [1] [Total: 14]

7 9701/33/F/M/16 © UCLES 2016 [Turn over 3 Qualitative Analysis At each stage of any test you are to record details of the following. ● colour changes seen ● the formation of any precipitate ● the solubility of such precipitates in an excess of the reagent added Where gases are released they should be identified by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling tube MUST be used. Rinse and reuse test-tubes and boiling tubes where possible. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given.

8 9701/33/F/M/16 © UCLES 2016 (a) FA 5 and FA 6 are solutions each containing one cation and one anion. Use a 1 cm depth of FA 5 or FA 6 in a test-tube to carry out the following tests on the two solutions and record your observations. test observations FA 5 FA 6 Add aqueous sodium hydroxide. Add aqueous ammonia. Add a 1 cm depth of dilute hydrochloric acid, then transfer the mixture into a boiling tube and warm gently. Add two or three drops of acidified aqueous potassium manganate(VII). Add a 1 cm depth of aqueous barium chloride or barium nitrate, then add dilute hydrochloric acid. Identify as many of the ions present in FA 5 and FA 6 as possible from your observations. If you are unable to identify any of the ions from your observations, write ‘unknown’ in the space. FA 5 FA 6 cation anion [8]

9 9701/33/F/M/16 © UCLES 2016 [Turn over (b) FA 7 is a solid with an anion containing the same element as one of the anions in either FA 5 or FA 6 but in a different oxidation state. Relevant anions are listed in the Qualitative Analysis Notes on page 11. Place a spatula measure of FA 7 in a boiling tube and add a 2 cm depth of distilled water. Shake the boiling tube to dissolve the solid and make a solution of FA 7. (i) Select reagents to test whether the anion in FA 7 contains the same element as the anion in FA 5. Carry out your test(s) on the solution of FA 7 and record your observations and conclusions in a suitable form in the space below. reagents for testing FA 7 … observations and conclusions (ii) Select reagents to test whether the anion in FA 7 contains the same element as the anion in FA 6. Carry out your test(s) on the solution of FA 7 and record your observations and conclusions in a suitable form in the space below. reagents for testing FA 7 … observations and conclusions [5] [Total: 13]

10 9701/33/F/M/16 © UCLES 2016 Qualitative Analysis Notes Key: [ppt. = precipitate] 1 Reactions of aqueous cations ion 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 heating – barium, Ba2+(aq) faint white ppt. is nearly always observed unless reagents are pure no ppt. calcium, Ca2+(aq) white ppt. with high [Ca2+(aq)] no ppt. chromium(III), Cr3+(aq) grey-green ppt. soluble in excess grey-green ppt. insoluble in excess copper(II), Cu2+(aq) pale blue ppt. insoluble in excess 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

11 9701/33/F/M/16 © UCLES 2016 2 Reactions of anions ion 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 ppt. with Ag+(aq) (partially soluble in NH3(aq)) iodide, I –(aq) gives 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; NO liberated by dilute acids (colourless NO → (pale) brown NO2 in air) sulfate, SO4 2–(aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acids) sulfite, SO3 2–(aq) gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids) 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

12 9701/33/F/M/16 © UCLES 2016 To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk 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 – 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 –

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the March 2016 series 9701 CHEMISTRY 9701/33 Paper 3 (Advanced Practical Skills), maximum raw mark 40 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 will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the March 2016 series for most Cambridge IGCSE® and Cambridge International A and AS Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – March 2016 9701 33 © Cambridge International Examinations 2016 question indicative material mark total 1 (a) I All thermometer readings and mass of FA 2 recorded. Do not award if mass of FA 2 > 0.50 g. 1 [4] II All temperatures recorded to 0.5 °C. 1 Award III and IV if within ranges given of supervisor’s value. supervisor’s ∆T / °C III IV ⩾ 46.0 ± 5.0 ± 2.5 36.0–45.5 ± 4.0 ± 2.0 26.0–35.5 ± 3.0 ± 1.5 16.0–25.5 ± 2.0 ± 1.0 6.0–15.5 ± 1.0 ± 0.5 < 6.0 ± 0.5 – 2 (b) I Axes labelled with units and uniform scale chosen to use more than half of each axis including 10 °C above the highest recorded temperature. 1 [4] II All recorded points plotted (minimum 9). 1 III Appropriate lines of best fit drawn: • best fit lines must be or a smooth curve; • Points not on the line must be balanced on either side of the best- fit line and any points ringed or labelled as anomalous ignored. IV Lines extrapolated and correct value (within 0.5 °C) of ∆T read from graph. 1 1 (c) (i) Correctly calculates Q = 25 × 4.2 × ∆T from (b). 1 [3] (ii) Correct expression for value of enthalpy change − × = × 24.3 mass in 1000 (c)(i) (a) (ignore sign) 1 Negative sign and both answers recorded to 2–4 sig. fig. and no rounding to 1 sig. fig. during calculation (unless exact value). 1 (d) Incorrect, as the acid was in excess already. 1 [1] (e) Any one from: • use lid or use specified extra insulation to reduce heat losses (by convection or conduction); • use a pipette or burette for FA 1 to reduce % error / as more accurately calibrated (owtte); • use magnesium turnings / powder so reaction complete sooner as there is heat loss while magnesium ribbon is still reacting; • use lid or plastic cup with higher walls to reduce acid spray; 1 [1]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – March 2016 9701 33 © Cambridge International Examinations 2016 question indicative material mark total 2 (a) I Initial and final burette readings and volume added recorded for rough titre and accurate titre details tabulated. 1 [7] II Initial and final burette readings recorded and volume of FA 4 added recorded for each accurate titration. All headings and units correct for accurate titrations: • initial / final (burette) reading / volume or reading / volume at start / finish • volume / FA 4 added / used or titre • (cm3) or / cm3 or in cm3 or cm3 by every entry. 1 III All accurate burette readings are recorded to the nearest 0.05 cm3. 1 IV Has two uncorrected, accurate titres within 0.1 cm3. 1 V, VI and VII Award V, VI and VII for δ ⩽ 0.20 cm3 Award V and VI for 0.20 cm3 < δ ⩽ 0.30 cm3 Award V for 0.30 cm3 < δ ⩽ 0.50 cm3 (b) Mean titre correctly calculated from clearly selected values. • Candidates must average two (or more) 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 readings selected. • The mean should normally be quoted to 2 d.p. rounded to the nearest 0.01. Note: the candidate’s mean will sometimes be marked as correct even if it is different from the mean calculated by the examiner for the purpose of assessing accuracy. 1 [1] (c)(i)(ii) Correctly calculates × 0.100 1000 (b) and (ii) = (i) 1 [5] (iii) (iv) Correct expression × × 1000 10 25 (c)(ii) mol Mg = mass in 1(a) / 24.3 and mol HCl = (c)(iii) × 25 / 1000 mol HCl > 2 × mol Mg (owtte) so the statement is correct. Allow ecf from incorrect (iii). Final answers (i), (ii) and (iii) to 3 or 4 sig. fig. and no rounding errors. 1 1 1 1

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – March 2016 9701 33 © Cambridge International Examinations 2016 question indicative material mark total (d) Correct expression × 0.1 100 (b) and answer to minimum 2 sig. fig. / correct answer to minimum 2 sig.fig. and FA 3 (is measured more accurately). Allow ecf from (b) > 41.67 cm3 then FA 4 (is measured more accurately). 1 [1] test observations FA 5 FA 6 NaOH no reaction / no change / no ppt white ppt, soluble in excess NH3 no reaction / no change / no ppt white ppt, insoluble in excess HCl (warm) blue solution brown gas / gas turning brown / gas turns blue litmus red / bleaches no reaction / no change H+ / MnO4 – decolourises / purple to colourless or (solution) stays colourless stays purple / pink or changes to purple / pink Ba2+ / HCl no reaction / no change / no ppt white ppt, insoluble in HCl question indicative material mark total FA 5 is NaNO2; FA 6 is Al2(SO4)3; FA 7 is Na2SO3 (Na2S2O5) 3 (a) Observations fully correct for both FA 5 and FA6 for NaOH. 1 [8] Observations fully correct for both FA 5 and FA6 for NH3. 1 Observation of blue solution or brown gas with FA 5 and no reaction with FA 6 for HCl. 1 Observations fully correct for both FA 5 and FA6 for H+ / MnO4 –. 1 Observations fully correct for both FA 5 and FA6 for Ba2+ / HCl. 1 Cations: FA 5 unknown and FA 6 Al 3+ / aluminium Anions: FA 5 NO2‒ / nitrite FA 6 SO4 2‒ / sulfate 1 1 1

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – March 2016 9701 33 © Cambridge International Examinations 2016 question indicative material mark total (b) (i) (Warm with) Al and NaOH and test gas with (damp) red litmus paper. 1 [5] No reaction and not nitrate / N / same element as FA 5. 1 (ii) BaCl 2 / Ba(NO3)2 and HCl / HNO3 or H+ / KMnO4 / acidified potassium manganate(VII) or any named acid, (warm) and test gas with H+ / KMnO4. 1 Ba2+ and acid: white ppt, soluble in acid or H+ / MnO4‒: solution decolourises / purple to colourless or acid and test gas with H+ / KMnO4: gas (evolved with acid) which decolourises H+ / MnO4– (paper). 1 FA 7 contains sulfite / SO3 2‒ 1