Cambridge A Level Chemistry 9701 — 2013 Oct/Nov 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 a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fl uid. 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 11 and 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 Advanced Practical Skills 1 October/November 2013 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confi dential Instructions UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certifi cate of Education Advanced Subsidiary Level and Advanced Level This document consists of 12 printed pages. [Turn over IB13 11_9701_33/4RP © UCLES 2013 *5651142458* Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/33/O/N/13 © UCLES 2013 For Examiner’s Use 1 In this experiment you are to determine the relative formula mass of an iron(II) salt by titration with potassium manganate(VII). FA 1 is the iron(II) salt. FA 2 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4. FA 3 is dilute sulfuric acid, H2SO4. (a) Method Preparing a solution of FA 1 ● Weigh the 250 cm3 beaker and record the mass in the space below. ● Add all the FA 1 provided to the beaker. Weigh the beaker with FA 1 and record the mass. ● Calculate the mass of FA 1 used and record this in the space below. ● Use a measuring cylinder to add approximately 100 cm3 of FA 3 to the beaker. Stir until all the solid has dissolved. ● Transfer the solution into the 250 cm3 volumetric (graduated) flask labelled FA 4. ● Wash out the beaker thoroughly using distilled water and add the washings to the volumetric flask. Make the solution up to the mark using distilled water. ● Shake the flask thoroughly to mix the solution before using it for your titrations. ● This solution of the iron(II) salt is FA 4. Titration ● Pipette 25.0 cm3 of FA 4 into a conical flask. ● Use a measuring cylinder to add 20 cm3 of FA 3 to the flask. ● Fill the burette with FA 2. ● Titrate FA 4 with FA 2 until the solution changes to a permanent pink colour. ● Perform a rough titration and record your burette readings in the space below. The rough titre is … cm3.

3 9701/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use I II III IV V VI VII ● 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 FA 2 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 have obtained this value. 25.0 cm3 of FA 4 required … cm3 of FA 2 [1]

4 9701/33/O/N/13 © UCLES 2013 For Examiner’s Use (c) Calculations Show your working and appropriate signifi cant fi gures in the fi nal answer to each step of your calculations. (i) Calculate the number of moles of potassium manganate(VII) present in the volume of FA 2 calculated in (b). moles of KMnO4 = … mol (ii) The half-equation for the reduction of a manganate(VII) ion is: MnO4 – + 8H+ + 5e– → Mn2+ + 4H2O Give the half-equation for the oxidation of an iron(II) ion to an iron(III) ion. … Therefore, 1 mole of manganate(VII) ions reacts with 5 moles of iron(II) ions. (iii) Calculate the number of moles of iron(II) ions present in 25.0 cm3 of solution FA 4. moles of Fe2+ in 25.0 cm3 of FA 4 = … mol (iv) Calculate the number of moles of iron(II) ions present in 250 cm3 of solution FA 4. moles of Fe2+ in 250 cm3 of FA 4 = … mol (v) In 1 mole of the iron(II) salt, FA 1, there is 1 mole of iron(II) ions. Use the mass of FA 1 you weighed out to calculate the relative formula mass of the iron(II) salt. relative formula mass = … [5] I II III IV V

5 9701/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (d) (i) A 25 cm3 pipette is accurate to ±0.06 cm3. Calculate the maximum percentage error when the pipette was used to measure solution FA 4. percentage error in measuring FA 4 = … % (ii) State the maximum error in the mass of the 250 cm3 beaker that you recorded in (a). maximum error = … g (iii) Calculate the maximum percentage error in the mass of FA 1 used in (a). maximum percentage error = … % [2] [Total: 15]

6 9701/33/O/N/13 © UCLES 2013 For Examiner’s Use I II III IV V VI 2 In this experiment you are to determine the formula of hydrated barium chloride, FA 5, by heating to remove the water of crystallisation. You will heat two separate samples. The anhydrous barium chloride does not decompose when heated. FA 5 is hydrated barium chloride, BaCl 2.xH2O (a) Method Record all weighings, in an appropriate form, in the space below. ● Record the mass of the empty crucible without its lid. ● Add between 2.0 and 2.4 g of FA 5 into the crucible. Record the mass of the crucible and its contents. ● Use a pipe-clay triangle to support the crucible and contents on a tripod. ● Heat the crucible and its contents gently for about one minute with the lid off. Then heat strongly for a further four minutes. ● Put the lid on the crucible and leave to cool for approximately 10 minutes. While you are waiting for the crucible to cool, start work on Question 3. ● When the crucible is cool, remove the lid, and weigh the crucible with the residue. ● Record the mass of anhydrous barium chloride remaining in the crucible after heating and the mass of water lost. ● To prepare for the second experiment, use a spatula to remove the residue from the crucible into the beaker labelled waste. ● Reweigh the empty crucible without its lid. ● Carry out the experiment again. This time use between 1.5 and 1.9 g of FA 5. [6]

7 9701/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (b) Calculation Show your working in each step. (i) Calculate the mean number of moles of water removed from the hydrated salt in the experiments. (Ar : H, 1.0; O, 16.0) moles of H2O = … mol (ii) Calculate the mean number of moles of anhydrous barium chloride produced in the experiments. (Ar : Ba, 137; Cl, 35.5) moles of BaCl 2 = … mol (iii) Calculate the value of x in the formula of hydrated barium chloride, BaCl 2.xH2O. x = … [3] (c) (i) Suggest how the experimental procedure could be modifi ed to ensure that all of the water of crystallisation had been removed by heating hydrated FA 5. … … … (ii) Do you think that the results from your two experiments are consistent with each other? Justify your answer by carrying out appropriate calculations. [3] [Total: 12]

8 9701/33/O/N/13 © UCLES 2013 For Examiner’s Use 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 identifi ed 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) FA 5 is hydrated barium chloride. FA 6 is the same iron(II) salt used in Question 1. It contains one other cation and one anion. (i) Place a small spatula measure of FA 6 into a test-tube. Dissolve the solid in about a 5 cm depth of distilled water. Use the solution for the following tests. test observations To a 1 cm depth of aqueous FA 6 in a boiling tube, add aqueous sodium hydroxide until no further change occurs, then heat the mixture carefully. Dissolve a few crystals of FA 5 in a 1 cm depth of distilled water in a test-tube. Add a 1 cm depth of FA 6, then add excess dilute hydrochloric acid to the mixture.

9 9701/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (ii) Identify the ions present in FA 6. cations: Fe2+ and … anion: … (iii) Give the ionic equation for the reaction of iron(II) ions with hydroxide ions. … (iv) Place a small spatula measure of FA 6 into a hard-glass test-tube. Heat gently, then strongly, until no further change is observed. Record your observations in the space below. [7]

10 9701/33/O/N/13 © UCLES 2013 For Examiner’s Use (b) FA 7, FA 8 and FA 9 are aqueous solutions. Each contains one cation and one anion. FA 3 is dilute sulfuric acid, H2SO4. Mix pairs of solutions so that you can complete the table below. For each test, use 1 cm depths of each solution in clean test-tubes. Record your observations in the table. FA 7 FA 8 FA 9 FA 3 FA 7 FA 8 From your observations, complete the following statements. The anion in FA 7 is … The cation in FA 8 is … The anion in FA 9 is … [6] [Total: 13]

11 9701/33/O/N/13 © UCLES 2013 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) no ppt. (if 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 lead(II), Pb2+(aq) white ppt. soluble in excess white 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 [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]

12 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. 9701/33/O/N/13 © UCLES 2013 2 Reactions of anions ion reaction carbonate, CO3 2– CO2 liberated by dilute acids chromate(VI), CrO4 2–(aq) yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) chloride, Cl –(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) bromide, Br –(aq) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) iodide, I –(aq) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)); gives yellow ppt. with Pb2+(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) or with Pb2+(aq) (insoluble in excess dilute strong acids) sulfi te, SO3 2–(aq) SO2 liberated with dilute acids; 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 sulfur dioxide, SO2 turns acidifi ed aqueous potassium dichromate(VI) from orange to green

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2013 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 October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE A LEVEL – October/November 2013 9701 33 © Cambridge International Examinations 2013 Question Sections Indicative material Mark Total 1 (a) PDO Layout I The following data must be given • mass of solid used (or both weighings) • volume for rough titre (or both readings) • initial and final readings for two (or more) accurate titrations. 1 PDO Recording II Appropriate headings for all data given in weighing and accurate titration tables and g and cm3 units. • mass/weight (of) beaker (empty) • mass/weight (of) beaker + FA 1/solid • initial/start (burette) reading/volume • final/end (burette) reading/volume • titre or volume/FA 2 used/added • unit: /cm3 or (cm3) or in cm3 or cm3 for each volume If g and/or cm3 units are not given in the heading, every entry in the table must have the correct unit. 1 PDO Recording III All accurate burette readings (including 0.00) are to the nearest 0.05 cm3. The need to record to 0.05 applies only to the burette readings and not to the recorded titres. Do not award this mark if: • 50(.00) is used as an initial burette reading or • more than one final burette reading is 50.(00) or • any burette reading is greater than 50.(00). 1 MMO Decision IV There are two uncorrected accurate titres within 0.10 cm3. Do not include a reading if it is labelled “rough”. 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 initial two titres, unless a further titration, within 0.1 cm3 of any other, has also been carried out. Do not award the mark if any ‘accurate’ burette readings (apart from initial 0) are given to zero dp. 1

Page 3 Mark Scheme Syllabus Paper GCE A LEVEL – October/November 2013 9701 33 © Cambridge International Examinations 2013 Question Sections Indicative material Mark Total (a) (cont) MMO Quality Award V, VI and VII if δ ≤ 0.03 (cm3 g–1) i.e. three Q marks. Award V and VI if 0.03 < δ ≤ 0.06 i.e. two Q marks. Award V, only, if 0.06 < δ ≤ 0.10 i.e. one Q mark. Spread penalty: if the two “best” (corrected) titres used by the Examiner were ≥ 0.50 cm3 apart, cancel one Q mark. 1 1 1 [7] (b) MMO Decision Check mean titre is correctly calculated from clearly selected values (ticks or working). • Candidate 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 dp rounded to the nearest 0.01. [e.g. 26.667 must be rounded to 26.67] Two special cases where the mean may not be to 2 dp: allow mean to 3 dp only for 0.025 or 0.075 e.g. 26.325; allow mean to 1 dp if all accurate burette readings were given to 1 dp (ignoring initial given as 0) and the mean is exactly correct. [e.g. 26.0 and 26.2 = 26.1 is correct but 26.0 and 26.1 = 26.1 is incorrect.] Do not award this mark if: • the rough titre was used to calculate the mean; • candidate carried out only 1 accurate titration; • burette readings were incorrectly subtracted to obtain any of the accurate titre values; • all burette readings (resulting in titre values used in calculation of mean) are integers. 1 [1] (c) (i) ACE Interpretation I Correctly calculates No. of moles of KMnO4 = 0.0200 x (b)/1000 1 (ii) ACE Conclusion II Fe2+
Fe3+ + e– / 5Fe2+
5Fe3+ + 5e– 1 (iii) + (iv) PDO Display III Correct working shown in (iii) and (iv). The answer to (i) should be multiplied by 5 to give (iii). The answer to (iii) should be multiplied by 10 to give (iv). 1 (v) ACE Interpretation IV Correct calculation of relative formula mass. Mr = correct mass of FA 1 used/answer to (iv) 1

Page 4 Mark Scheme Syllabus Paper GCE A LEVEL – October/November 2013 9701 33 © Cambridge International Examinations 2013 Question Sections Indicative material Mark Total (v) (cont) PDO Display V All answers are quoted to 3 or 4 significant figures. A minimum of three answers is needed to qualify. 1 [5] (d) (i) ACE Interpretation % error for pipette = 0.06/25 × 100 = 0.24% (or 0.240%) 1 (ii) + (iii) ACE Interpretation If balance displays to 1 decimal place: error in balance reading is ±0.05 g or ±0.1(0) g. If balance displays to 2 decimal places: error in balance reading is ±0.005 g or ±0.01 g. If balance displays to 3 decimal places: error in balance reading is ±0.0005 g or ±0.001 g. % error = 2 × balance error (above)/mass of FA 1 used × 100 Correct answer is not required, but if the “× 100” factor was omitted, a correctly calculated % error answer scores the mark. 1 [2] [Total: 15] 2 (a) MMO Collection I The masses of FA 5 used by the candidate were between 2.0–2.4 g (expt 1) and 1.5–1.9 g (expt 2). 1 PDO Display II Suitable headings for a table or list, shown completely for at least one experiment carried out. If 2 experiments, all headings must be correct. • (mass of) empty crucible • (mass of) crucible + FA 5 • (mass of) crucible + residue / FA 5 after heating • (mass of) residue (owtte) • mass lost or (mass of) water lost. and unit was given “covering” every weighing; Unit: /g or (g) or in grams or g following each weighing 1 PDO Recording III Records all weighings consistently to at least 1 dp. A minimum of three weighings are needed. 1 Accuracy (Q) marks for gravimetric experiment – 3 marks available Examiner checks working for mass of residue and mass of water and expresses the ratio mass of hydrated solid/mass of water to 2 dp for each experiment. The expected ratio = 244/36 = 6.78.

Page 5 Mark Scheme Syllabus Paper GCE A LEVEL – October/November 2013 9701 33 © Cambridge International Examinations 2013 Question Sections Indicative material Mark Total (a) (cont) MMO Quality Award IV if the ratio in expt 1 is between 6.30 and 7.25. Award V If the ratio in expt 2 is between 6.30 and 7.25. Award VI If the ratio in both of experiments 1 and 2 is between 5.90 and 7.65, inclusive. 1 1 1 [6] (b) (i) MMO Display Correct expression for the number of moles of water lost (from mass as recorded) or correct answer. 1 (ii) ACE Interpretation Correct expression for the number of moles of residue with correct masses of anhydrous salt and 208 and answer expressed to 2–4 sf or correct answer and 2–4 sf If only one expt carried out then correct calculation for number of moles of residue expressed to 2–4 sig fig. 1 (iii) ACE Interpretation Correct calculation of (i) ÷ (ii) to give answer as an integer. (should be x = 2) 1 [3] (c) (i) ACE Improvements Heat to constant mass (owtte) 1 (ii) ACE Interpretation An attempt to “scale” mass loss to the mass of FA 5 used or to calculate x separately for the two experiments. 1 ACE Conclusion Uses calculated values to comment sensibly on the consistency the results. 1 [3] [Total: 12] FA 6 is (NH4)2Fe(SO4)2(s); FA 7 is Na2CO3(aq); FA 8 is Pb(NO3)2(aq); FA 9 is K2CrO4(aq) 3 (a) (i) MMO Collection Green precipitate and ppt insoluble in excess NaOH/ppt turning brown (in air / on standing). 1 MMO Decision (When heated with NaOH) gas / NH3 turns red litmus to blue. 1 MMO Collection (With BaCl2), white precipitate forms and insoluble in HCl. 1 (ii) ACE Conclusion FA 6 contains ammonium ions and sulfate ions. (correct evidence needed for each ion in the observations table). 1 (iii) ACE conclusion Fe2+ + 2OH-
Fe(OH)2 1

Page 6 Mark Scheme Syllabus Paper GCE A LEVEL – October/November 2013 9701 33 © Cambridge International Examinations 2013 Question Sections Indicative material Mark Total (iv) MMO collection Any two of • Solid goes paler / loses green colour (at first) and then becomes brown (on strong heating) • Condensation / water vapour / steam produced • (Gas/NH3) turns red litmus blue. 1 1 [7] (b) MMO collection FA 7 + FA 3 : Fizzing/effervescence and limewater goes milky. 1 FA 8 + FA 3 and FA 8 + FA 7 : white precipitate obtained in both cases 1 FA 9 + FA 3: (solution) turns orange FA 9 + FA 7: statement of no change/yellow solution FA 9 + FA 8: (bright) yellow precipitate/solid (formed). All three observations in the third column must be correct. 1 ACE Conclusion FA 7 contains carbonate ions (evidence needed) / CO3 2– 1 FA 8 contains lead ions or barium ions (or both) (evidence needed) / Pb2+ / Ba2+ 1 FA 9 contains chromate(VI) ions / CrO4 2– 1 [6] [Total: 13]