Cambridge A Level Chemistry 9701 — 2014 May/June Paper 3 · Variant 3

This document consists of 11 printed pages and 1 blank page. [Turn over IB14 06_9701_33/4RP © UCLES 2014  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 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 10 and 11. 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 May/June 2014 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confi dential Instructions Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level Session Laboratory For Examiner’s Use 1 2 3 Total

2 9701/33/M/J/14 © UCLES 2014 I II III IV V VI VII 1 You are to determine, by titration, the change in oxidation number of a transition metal ion, M2+, when reacted with acidifi ed potassium manganate(VII). FA 1 is 0.0200 mol dm–3 potassium manganate(VII), KMnO4. FA 2 is 0.0530 mol dm–3 transition metal salt, MSO4. FA 3 is 1.0 mol dm–3 sulfuric acid, H2SO4. (a) Method ● Fill the burette with FA 1. ● Pipette 25.0 cm3 of FA 2 into the conical flask. ● Use the measuring cylinder to add 25 cm3 of FA 3 into the conical flask. ● Carry out a rough titration and record your burette readings in the space below. Add FA 1 until the contents of the flask turn a permanent pale pink 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 below, in a suitable form, all of your burette readings and the volume of FA 1 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 2 required … cm3 of FA 1. [1]

3 9701/33/M/J/14 © UCLES 2014 [Turn over I II III IV V (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 1 calculated in (b). moles of KMnO4 = … mol (ii) Calculate the number of moles of MSO4 in 25.0 cm3 of FA 2. moles of MSO4 in 25.0 cm3 = … mol (iii) Use your answers to (i) and (ii) to calculate the number of moles of MSO4 that react with 1 mole of KMnO4. moles of MSO4 = … mol (iv) Two possible equations for the reaction of acidifi ed KMnO4 with MSO4 are below. equation 1 2KMnO4 + 10MSO4 + 8H2SO4  K2SO4 + 2MnSO4 + 5M2(SO4)3 + 8H2O equation 2 2KMnO4 + 5MSO4 + 8H2SO4  K2SO4 + 2MnSO4 + 5M(SO4)2 + 8H2O State and explain which of these two equations is consistent with your answer to (iii). … … (v) Use your answer to (iv) to state the oxidation number of the transition metal M in the product of the reaction. … [5] [Total: 13]

4 9701/33/M/J/14 © UCLES 2014 2 You will determine the enthalpy change, H, for the reaction between magnesium and dilute sulfuric acid. The equation for the reaction is given below. Mg(s) + H2SO4(aq)  MgSO4(aq) + H2(g) FA 3 is 1.00 mol dm–3 sulfuric acid, H2SO4. two different coiled lengths of magnesium ribbon, Mg. (a) Method Read through the method before starting any practical work and prepare a table for your results in the space below. ● Weigh the shorter piece of magnesium ribbon and record its mass. ● Support the plastic cup in the 250 cm3 beaker. ● Use the measuring cylinder to transfer 50 cm3 of FA 3 into the plastic cup. ● Place the thermometer in the FA 3 in the plastic cup and record the initial temperature. ● Add the shorter piece of magnesium ribbon into the plastic cup. Ensure that all of the magnesium is in contact with the acid. (Care: acid spray may occur.) ● Stir the mixture and record the maximum temperature. ● Empty and rinse the plastic cup. Shake out any excess water. ● Repeat the experiment using the longer piece of magnesium ribbon and record all your data. Results [4] (b) Calculations Show your working and appropriate signifi cant fi gures in the fi nal answer to each step of your calculations. (i) Show by calculation that the sulfuric acid, FA 3, was used in excess in both experiments. (Ar: Mg, 24.3)

5 9701/33/M/J/14 © UCLES 2014 [Turn over (ii) State an observation which confi rms that the sulfuric acid, FA 3, was in excess. … (iii) Calculate the heat energy produced when the shorter piece of magnesium was added to FA 3. (Assume that 4.3 J of heat energy changes the temperature of 1.0 cm3 of solution by 1.0 C.) heat energy produced = … J (iv) Calculate the enthalpy change, in kJ mol–1, for the reaction between the shorter piece of magnesium and the sulfuric acid. enthalpy change = … … kJ mol–1 (sign) (value) (v) Calculate the heat energy produced when the longer piece of magnesium was added to FA 3. (Assume that 4.3 J of heat energy changes the temperature of 1.0 cm3 of solution by 1.0 C.) heat energy produced = … J (vi) Calculate the enthalpy change, in kJ mol–1, for the reaction between the longer piece of magnesium and the sulfuric acid. enthalpy change = … … kJ mol–1 (sign) (value) [5] (c) (i) What is the maximum error in a reading of the thermometer used in this experiment? maximum error = … C. (ii) Which of your temperature changes has the higher percentage error? … (iii) Calculate this maximum percentage error. maximum percentage error in the temperature change = … % [1]

6 9701/33/M/J/14 © UCLES 2014 (d) Apart from errors due to heat loss and thermometer readings, suggest another signifi cant source of error in this experiment. State what improvement could be made to the procedure to reduce this error. … … … [2] [Total: 12]

7 9701/33/M/J/14 © UCLES 2014 [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 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. 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. (a) FA 4, FA 5 and FA 6 are solutions, each containing one transition metal ion. One of the solutions also contains the ammonium ion. All the cations present are listed in the Qualitative Analysis Notes on page 10. (i) Carry out the following tests on the three solutions. test observations To a 1 cm depth of FA 4 in a test-tube, add FA 1, aqueous potassium manganate(VII), dropwise. To a 1 cm depth of FA 5 in a test-tube, add FA 1, aqueous potassium manganate(VII), dropwise. To a 1 cm depth of FA 6 in a test-tube, add FA 1, aqueous potassium manganate(VII), dropwise. (ii) State which solution(s) contain ions which have been oxidised. … [4] I II III IV

8 9701/33/M/J/14 © UCLES 2014 (b) (i) Select a reagent or reagents to identify all the cations present in the three solutions. reagent(s) … Carry out experiments using your reagent(s) on each of FA 4, FA 5 and FA 6 and record your observations in a suitable form in the space below. (ii) Use your observations to identify the cations present in the three solutions. FA 4 contains … FA 5 contains … FA 6 contains … [8] I II III IV V VI VII VIII

9 9701/33/M/J/14 © UCLES 2014 [Turn over (c) Each of the solutions FA 4, FA 5 and FA 6 contains either a chloride or a sulfate ion. (i) Choose a reagent or reagents to identify which solution(s) contain chloride ions. reagent(s) … Use your reagent(s) to carry out a test on each of FA 4, FA 5 and FA 6 and record your results in the space below. (ii) State which solution(s) contain a chloride ion. … [3] [Total: 15]

10 9701/33/M/J/14 © UCLES 2014 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 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/M/J/14 © UCLES 2014 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) 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 manganate(VII) from purple to colourless

12 9701/33/M/J/14 BLANK PAGE © UCLES 2014 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. 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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2014 series 9701 CHEMISTRY 9701/33 Paper 3 (Advanced Practical Skills 1), 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 May/June 2014 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9701 33 © Cambridge International Examinations 2014 Question Sections Indicative material Mark Total 1 (a) PDO Layout 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 × 2 box) 1 MMO Collection II Appropriate headings and units for all accurate data. and volume FA 1 added recorded for each accurate titre. Headings should match readings. • initial/start (burette) reading/volume • final/end (burette) reading/volume • titre or volume/FA 1 used/added (not “difference”) unit: /cm3 or (cm3) or in cm3 or cm3 for each entry 1 PDO Recording III All accurate burette readings recorded to 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 • more than one final burette reading is 50.(00) • any burette reading is greater than 50.(00). 1 MMO Decisions IV Has two uncorrected, accurate titres within 0.1 cm3. Do not include a reading labelled ‘rough’. Do not award this mark if, having performed two titres within 0.1 cm3, a further titration is performed that is more than 0.1 cm3 from the closer of the two initial titres unless further titrations within 0.1 cm3 of any other have also been carried out. Do not award the mark if any ‘accurate’ burette readings (apart from initial 0) are given to zero dp. 1 All burette readings should be rounded to the nearest 0.05 cm3. Subtractions should be checked. The ‘best’ titres should be selected using the hierarchy: two (or more) identical, then two (or more) within 0.05 cm3 , then two (or more) within 0.1 cm3, etc. Examiner compares candidate mean titre with Supervisor mean titre. (a) MMO Quality V, VI and VII Award V, VI and VII for a difference from Supervisor, δ ≤ 0.20 cm3 Award V and VI for 0.20 < δ ≤ 0.30 cm3 Award V only for 0.30 < δ ≤ 0.50 cm3 Spread penalty: if the two ‘best’ titres used by the Examiner are ≥ 0.50 cm3 apart cancel one of the Q marks. 3 [7]

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9701 33 © Cambridge International Examinations 2014 Question Sections Indicative material Mark Total (b) ACE Interpretation Candidate must average two (or more) titres that are all within 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. 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 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. 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) PDO Display I Uses the expression 1000 0.0200 (b) × in (i) (or answer correct to 3 or 4 sf) 1 ACE Interpretation II Correctly evaluates 1000 25 0.0530 × in (ii) (to 3 or 4 sf) 1 III (i) (ii) to answer to answer in (iii) and correct answer to 2, 3 or 4 sf 1 IV Equation 2 as ratio is 5:2 or 2½ and reference to their answer in (iii) Allow ecf 1 ACE Conclusion V Oxidation state = (+)4 in (v) from equation 2 Allow ecf ((+)3) 1 [5] Qn 1 Total [13]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9701 33 © Cambridge International Examinations 2014 Question Sections Indicative material Mark Total 2 (a) PDO Recording Four thermometer readings and two masses tabulated with correct headings and units. (mass/g or (g) or in g; temperature/temp/T/°C, etc.) If units are omitted from the headings then they must appear next to each entry in the table. 1 Display Consistent dp for balance readings and (minimum 3) thermometer readings to ×.0/×.5. 1 Correct temperatures to nearest 0.5 °C. Examiner calculates ∆T for longer piece of magnesium for Supervisor and candidate. (a) MMO Quality Award one mark if the difference between candidate and Supervisor is ≤ 2.0 °C. Award second mark if the difference between candidate and Supervisor is ≤ 1.0 °C. 1 1 [4] (b) ACE Interpretation I 1000 1.00 50 24.3 Mg longer mass × < in (i) 1 MMO Collection II No solid/metal left/all Mg disappeared/dissolved in (ii) 1 ACE Interpretation III Expression 50 × 4.3 × ∆T or correct answers in (iii) and (v) 1 PDO Display IV Uses Mg/24.3 shorter mass to answer (iii) in (iv) and Mg/24.3 longer mass to answer (v) in (vi) Allow ecf from (i) 1 ACE Interpretation V Correct answers given to 2–4 sf in kJ and minus signs in (iv) and (vi) 1 [5] (c) ACE Interpretation (2 × 0.5/smaller ∆T) × 100 for shorter piece of Mg in (iii) 1 [1] (d) ACE Interpretation Improvements Mass of/weighing Mg (ribbon) or volume of H2SO4 used or corrosion on Mg Use greater mass/balance to more dp or use burette/pipette (to measure volume) or use sand paper or emery paper or use lid or taller beaker or taller cup to prevent acid spray 1 1 [2] Qn 2 Total [12]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9701 33 © Cambridge International Examinations 2014 Question Sections Indicative material Mark Total FA 4 is FeCl3(aq) FA 5 is MnSO4(aq) FA 6 is (NH4)2Fe(SO4)2(aq) 3 (a) (i) MMO Collection I (Solution) turns pink/pink-brown/brown/purple or no reaction/no change 1 II (Purple decolourised and) (dark) brown ppt 1 III (Purple) decolourised 1 (ii) ACE Conclusion IV (FA 5 and) FA 6 1 [4] (b) (i) PDO Layout I NaOH on answer line and unambiguous table of results including observations for excess NaOH with all three 1 MMO Collection II Brown/orange/red-brown/rust ppt (insoluble in excess NaOH with FA 4) 1 III Off-white/buff/light brown ppt (insoluble in excess NaOH with FA 5) 1 IV Green/dirty green ppt (insoluble in excess NaOH with FA 6) 1 V ppt with FA 5 darkens/turns dark(er) brown and ppt with FA 6 darkens/turns green-brown/brown/orange-brown/ red-brown on standing 1 VI On warming/heating with NaOH gas evolved turns (damp) red litmus (paper) blue with FA 6 only 1 (ii) ACE Conclusion VII FA 4 contains Fe3+ and FA 5 contains Mn2+ and FA 6 contains Fe2+ 1 VIII FA 6 contains NH4 + 1 [8] (c) (i) MMO Decisions Selects AgNO3 or BaCl 2/Ba(NO3)2 1 MMO Collection AgNO3: FA 4 white ppt and no ppt/reaction with FA 5 and FA 6 or BaCl 2/Ba(NO3)2: white ppt with FA 5 and FA 6 and no ppt/reaction with FA 4 1 (ii) ACE Conclusion FA 4 (contains the chloride ion) 1 [3] Qn 3 Total [15]