Cambridge A Level Chemistry 9701 — 2016 May/June Paper 3 · Variant 4

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 9701/34 Paper 3 Advanced Practical Skills 2 May/June 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 11 printed pages and 1 blank page. [Turn over IB16 06_9701_34/4RP © UCLES 2016 *1069608282* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/34/M/J/16 © UCLES 2016 1 Borax is an alkali which has many uses. In this experiment you will determine x in the chemical formula of borax, Na2BxO7.10H2O, by titration with hydrochloric acid. FB 1 is a solution containing 15.5 g dm–3 of borax, Na2BxO7.10H2O. FB 2 is 2.00 mol dm–3 hydrochloric acid, HCl. methyl orange indicator (a) Method Dilution of FB 2 • Pipette 10.0 cm3 of FB 2 into the 250 cm3 volumetric flask. • Make the solution up to 250 cm3 using distilled water. • Shake the solution in the volumetric flask thoroughly. • This diluted solution of hydrochloric acid is FB 3. Label the volumetric flask FB 3. Titration • Fill the burette with FB 3. • Pipette 25.0 cm3 of FB 1 into a conical flask. • Add several drops of methyl orange. • 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 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 FB 3 added in each accurate titration. [7] (b) From your accurate titration results, obtain a suitable value for the volume of FB 3 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FB 1 required … cm3 of FB 3. [1] I II III IV V VI VII

3 9701/34/M/J/16 © UCLES 2016 [Turn over (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 hydrochloric acid present in the volume of FB 3 calculated in (b). moles of HCl = … mol (ii) 1 mole of borax is neutralised by 2 moles of hydrochloric acid. Calculate the number of moles of borax that react with the hydrochloric acid in (i). moles of borax = … mol (iii) Use your answer to (ii) to calculate the number of moles of borax in 1.00 dm3 of FB 1. moles of borax in 1.00 dm3 FB 1 = … mol (iv) Use your answer to (iii) and the information on page 2 to calculate the relative formula mass, Mr, of borax. Mr of borax = … (v) Calculate x in the formula of borax, Na2BxO7.10H2O. Use data from the Periodic Table on page 12. x = … [5] [Total: 13]

4 9701/34/M/J/16 © UCLES 2016 2 Some metal carbonates cannot be obtained in a pure state. For example magnesium carbonate exists in a ‘basic’ form, in which magnesium hydroxide is also present. One possible chemical formula of basic magnesium carbonate is MgCO3.Mg(OH)2.2H2O. When basic magnesium carbonate is heated, if the possible formula were correct, it would decompose as shown below. MgCO3.Mg(OH)2.2H2O(s) → 2MgO(s) + CO2(g) + 3H2O(g) In this experiment, you will decompose basic magnesium carbonate by heating it, and you will use your results to determine whether this possible formula is correct. FB 4 is basic magnesium carbonate. (a) Method Read through the method before starting any practical work and prepare a table for your results in the space below. • Weigh a crucible with its lid and record the mass. • Add 1.1-1.3 g of FB 4 to the crucible. Weigh the crucible and lid with FB 4 and record the mass. • Place the crucible on the pipe-clay triangle and remove the lid. • Heat the crucible and contents gently for about one minute. • Then heat the crucible and contents strongly for about four minutes. • Replace the lid and allow the crucible to cool for at least five minutes. • While the crucible is cooling, you may wish to begin work on Question 3. • Re-weigh the crucible and contents with lid. Record the mass. • Calculate, and record, the mass of FB 4 used and the mass of residue obtained. [5] I II III IV V

5 9701/34/M/J/16 © UCLES 2016 [Turn over (b) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Use your results to calculate the number of moles of magnesium oxide, MgO, obtained as residue. moles of MgO obtained = … mol (ii) Use your answer to (i), with the equation on page 4 and the mass of FB 4 you used, to calculate the relative formula mass, Mr, of basic magnesium carbonate. Mr of basic magnesium carbonate (from experiment) = … (iii) Use data from the Periodic Table to calculate the relative formula mass, Mr, of basic magnesium carbonate from its possible formula, MgCO3.Mg(OH)2.2H2O. Mr of basic magnesium carbonate (from formula) = … (iv) If the relative formula mass of basic magnesium carbonate obtained from your experiment is within 2.5% of the answer in (iii), this is good evidence that the possible formula, MgCO3.Mg(OH)2.2H2O, is correct. Does your experiment support the possible formula? Give a reason for your answer. … … [5]

6 9701/34/M/J/16 © UCLES 2016 (c) Evaluation (i) State one way in which the accuracy of the experimental procedure could have been improved using the same mass of FB 4. Explain your answer. … … … … … (ii) A student carried out the experiment twice using different masses of FB 4. He used the mean mass of FB 4 and the mean mass of magnesium oxide obtained to calculate the relative formula mass of basic magnesium carbonate. Instead of doing this, he could have calculated the relative formula mass of basic magnesium carbonate from his two experiments separately. Suggest one advantage of carrying out separate calculations for each experiment. … … … … (iii) State the error when making one reading on your balance. error = … g Calculate the maximum percentage error in the mass of FB 4 used. percentage error = … % [4] [Total: 14]

7 9701/34/M/J/16 © UCLES 2016 BLANK PAGE [Turn over

8 9701/34/M/J/16 © UCLES 2016 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. 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. (a) FB 5, FB 6 and FB 7 are solutions, each of which contain one cation and one anion. The anions present are all listed on page 11. Use a 1 cm depth of these solutions in a test-tube for each of the following tests. Complete the table below. test observations FB 5 FB 6 FB 7 Add a 2 cm strip of magnesium ribbon. Add aqueous sodium hydroxide. Add an equal depth of aqueous potassium iodide. Add a few drops of FB 5. [5]

9 9701/34/M/J/16 © UCLES 2016 [Turn over (b) (i) From the observation made when potassium iodide was added to FB 6, suggest the identity of the cation in FB 6. Explain your conclusion. cation in FB 6 … explanation … … (ii) FB 5 gives no precipitate when aqueous ammonia is added. Suggest the identities of both ions in FB 5. cation in FB 5 … anion in FB 5 … (iii) Identify FB 7. … (iv) Give the ionic equation for the reaction between magnesium and FB 7. … [4] (c) FB 8 is a solid. Carry out the following tests on FB 8. Record your observations in each test. (i) Heat a small spatula measure of FB 8 gently in a hard-glass test-tube. observations … … … … (ii) To a 1 cm depth of hydrochloric acid in a test-tube, add a small spatula measure of FB 8. observations … … … … (iii) What conclusions, if any, can you make about the identities of the ions in FB 8? cation in FB 8 … anion in FB 8 … [4] [Total: 13]

10 9701/34/M/J/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 giving dark green solution 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 9701/34/M/J/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 9701/34/M/J/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. This document consists of 7 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CHEMISTRY 9701/34 Paper 34 Advanced Practical Skills 2 May/June 2016 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 will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2016 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 Question Indicative material Mark Total 1 (a) I Initial and final readings and titre value given for rough titre and initial and final readings for two (or more) accurate titrations (minimum of 2 x 2 box) 1 II Titre values recorded for accurate titrations and Appropriate headings for the accurate titration table and cm3 units. • initial / start burette reading / volume / value • final / end burette and reading / volume / value • titre or volume / FB3 and used / added • unit: / cm3 or (cm3) or in cm3 or cm3 (for each heading) 1 III All accurate burette readings are to the nearest 0.05 cm3. Do not award this mark if: • 50(.00) is used as an initial burette reading • more than one final burette reading is 50.(00) • any burette reading is greater than 50.(00) 1 IV There are two (or more) uncorrected, accurate titres within 0.10 cm3 • Do not award this mark if, having performed two titres within 0.1 cm3, a further titration is performed which is more than 0.10 cm3 from the closer of the two initial titres, unless a further titration, within 0.10 cm3 of any other, has also been carried out. • Do not award the mark if any “accurate” burette readings (apart from initial 0 cm3) are given to zero dp. 1 V, VI and VII Examiner rounds any accurate burette to the nearest 0.05 cm3, checks 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 titre, expressed to nearest 0.01 cm3. Accuracy marks are awarded as shown. Award V, VI and VII for δ ⩽ 0.30 (cm3) Award V and VI for 0.30 cm3 < δ ⩽ 0.60 (cm3) Award V for 0.60 cm3 < δ ⩽ 1.00 (cm3) 3 [7]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 Question Indicative material Mark Total (b) Candidate must take the average of two (or more) titres that are within a total spread of not more than 0.20 cm3. Working 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, rounded to the nearest 0.01. Two special cases where the mean may not be to 2 dp: • Allow mean expressed to 3 dp only for 0.025 or 0.075 (e.g. 26.325) • Allow mean if expressed to 1 dp if all accurate burette readings were given to 1 dp and the mean is exactly correct. (e.g. 26.0 and 26.2 = 26.1 is allowed) (e.g. 26.0 and 26.1 = 26.1 is incorrect – should be 26.05.) • 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) Correctly calculates n(HCl) used = 0.008 × b( ) 1000 1 [5] (ii) (iii) Correct use of factors n(borax) = 0.5 × answer (i) and n(borax) = 40 × answer (ii) 1 (iv) Correct use of (iii) and 15.5 Mr = 15.5 iii ( ) 1 (v) Correct expression x = (iv) −338 10.8 ( ) 1 All answers to 3 or 4 significant figures and if answer (v) is attempted it must be an integer 1 Question 2 [13]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 Question Indicative material Mark Total 2 (a) I Appropriate headings and units for the three balance readings • (Mass of) crucible (and lid) • (Mass of) crucible, (lid) and FB 4 (or “contents before heating”) • (Mass of) crucible, (lid) and residue / MgO / contents after heating / FB 4 after heating • Unit covering all balance readings and subtracted values if shown: / g, (g), in g or g (for each heading) 1 [5] II Masses recorded • Mass of FB 4 used was claimed to be between 1.1–1.3 g • All balance readings recorded to same number of decimal places (at least one dp) 1 III Mass of FB 4 and of residue • Mass of FB 4 used, correctly subtracted • Mass of residue, correctly subtracted 1 IV and V • Use corrected values • Examiner used corrected values and works out the ratio mass of FB 4/mass of MgO to 1 dp for the candidate Accuracy marks are awarded as shown. Award IV if ratio between 1.4–2.5 Award V if ratio between 1.7–2.3 2 (b) (i) Correctly calculates n(MgO) • mass of residue/40.3 • Answer must be expressed to 2, 3 or 4 significant figures 1 [5] (ii) Correct use of (i) and mass of FB 4 • n(FB 4) = answer (i)/2 • Mr = mass of FB 4 used/no of moles of FB 4 • An answer for Mr must be quoted to 2 or more significant figures 1 (iii) Mr calculated from Ar values in Periodic Table = 178.6 1 (iv) Correct expression shown 2.5/100 × Mr in (iii) (= 4.5, 4.47, 4.465) or expresses % difference of the two Mr values = │(iii) – (ii)│/(iii) × 100 or (iii) × 97.5/100 / (iii) × 102.5/100 to give range (= 174(.1) – 183(.1)) 1 Makes a correct statement (support / does not support / yes / no) about the accuracy of the possible formula, explained by whether the experimental Mr value is close to the answer in (iii). Numbers must be quoted or reference made to (ii) and (iii) 1

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 (c) (i) Improvement Heat (crucible and residue) to constant mass Accept a description of the procedure for the mark or heat more strongly / to a higher temperature or heat for longer so more is decomposed If a 1 dp balance is used allow use a balance weighing to more dp and to reduce % error (in weighing) / give more precise mass 1 [4] (ii) Conclusion To find out whether the two experiments are reliable / consistent / concordant or If the experiments do not agree then carry out a 3rd / another expt or If one experiment was inaccurate because it gave a poor Mr value it can be ignored 1 (iii) Error is 0.005 g or 0.01 g (if 2 dp balance was used) (If a 3 dp balance was used, error is 0.0005 or 0.001 g) (If a 1 dp balance was used, error is 0.05 or 0.1 g) 1 % = 100 × 2 × error / mass of FB 4 Accept correct expression or correct answer to 2, 3 or 4 significant figures 1 Question 2 [14]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 FB 5 is BaCl2; FB 6 is AgNO3; FB 7 is H2SO4; FB 8 is NaHCO3 3 (a) Three correct observations with Mg Three correct observations with NaOH Three correct observations with KI test FB 5 FB 6 FB 7 Mg no reaction / no change (ignore few bubbles (on Mg) / gas produced slowly) grey / black and ppt / solid / coating / deposit or Mg goes black / grey fizzing / bubbling / effervescence NaOH no change / no reaction / no ppt / (solution) stays colourless Allow white ppt / cloudy white soluble in excess is CON (dark) brown ppt soluble in excess is CON Allow brown ppt as final colour after a paler shade of brown but not a different colour (e.g. green / yellow / red) no change / no reaction / (solution) remains colourless / no ppt or temperature rises Allow heat produced but not exothermic KI no change / no reaction / (solution) remains colourless Accept pale yellow solution (pale) yellow ppt Allow greenish yellow (but not yellowish green) Allow cream-yellow no change / no reaction / (solution) remains colourless Accept pale yellow solution FB 5 white ppt white ppt (Mg) gas / H2 (evolved) pops with lighted splint / spill 3 [5] Two correct observations with FB 5 1 Correct hydrogen gas test 1

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9701 34 © Cambridge International Examinations 2016 (b) (i) Conclusion and reason Cation is silver / Ag+ (allow lead(II) / Pb2+) and Gives yellow precipitate (with iodide ions) or AgI (PbI2) produced 1 [4] (ii) Both conclusions about FB 5 are correct • cation – barium / Ba2+ • anion – chloride / Cl – 1 (iii) FB 7 is sulfuric acid / H2SO4 1 (iv) Mg + 2H+ → Mg2+ + H2 1 (c) (i) Any two observations from: • Condensation / water formed (inside test tube) • Steam liberated / hissing / (water) vapour produced / steamy / misty fumes • White residue / solid remains white / white solid formed 1 [4] Gas / CO2 turns lime water milky / white precipitate / cloudy white / chalky 1 (ii) Any two observations from: • Fizzing / bubbling / effervescence • Reaction is rapid / vigorous • Solid dissolves / colourless solution formed (at end) • Temperature drops / it gets colder 1 (iii) Both conclusions required • cation – not known / not transition metal • anion – carbonate / CO3 2‒ or hydrogencarbonate / HCO3‒ 1 Question 3 [13]