Cambridge A Level Chemistry 9701 — 2009 May/June Paper 3 · Variant 2

This document consists of 12 printed pages. SP (SHW 00157 2/08) T67843/4 © UCLES 2009 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level 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 fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You are advised to show all working in calculations. 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. * 2 6 4 5 1 2 6 0 1 4 * CHEMISTRY 9701/32 Paper 32 Advanced Practical Skills May/June 2009 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions For Examiner’s Use 1 2 3 Total Session Laboratory

2 9701/32/M/J/09 © UCLES 2009 For Examiner’s Use 1 You are provided with the following. FB 1 is 0.023 mol dm–3 potassium manganate(VII), KMnO4. FB 2 is aqueous ethanedioic acid, H2C2O4, made by dissolving the hydrated salt, H2C2O4.2H2O. You are also provided with the following. 1.0 mol dm–3 sulfuric acid, H2SO4 distilled water You are required to determine the concentration, in g dm–3, of hydrated ethanedioic acid, H2C2O4.2H2O, in FB 2. Dilution of FB 2 (a) By using a burette, measure between 42.50 cm3 and 43.00 cm3 of FB 2 into the 250 cm3 graduated flask, labelled FB 3. Record your burette readings and the volume of FB 2 added to the flask in the space below. Make up the contents of the flask to the 250 cm3 mark with distilled water. Place the stopper in the flask and mix the contents thoroughly by slowly inverting the flask a number of times. Titration Fill a second burette with FB 1. Pipette 25.0 cm3 of FB 3 into a conical flask. Use the measuring cylinder provided to add to the flask 25 cm3 of 1.0 mol dm–3 sulfuric acid and 40 cm3 of distilled water. Put the thermometer in the flask and heat the solution until the temperature is just over 65 °C. Carefully remove the thermometer and place the hot flask under the burette. If the neck of the flask is too hot to hold safely, use a folded paper towel to hold the flask. Run in 1 cm3 of FB 1. Swirl the flask until the colour of the potassium manganate(VII) has disappeared then continue the titration as normal until a permanent pale pink colour is obtained. This is the end-point. If a brown colour appears during the titration, reheat the flask to 65 °C. The brown colour should disappear and the titration can be completed as above. If the brown colour does not disappear on reheating, discard the solution and start the titration again. Perform a rough (trial) titration and sufficient further titrations to obtain reliable results. Record your titration results in the space below. Make certain that your recorded results show the precision of your working. [6] i ii iii iv v vi

3 9701/32/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (b) From your titration results obtain a volume of FB 1 to be used in your calculations. Show clearly how you obtained this volume. [1] Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (c) Calculate how many moles of KMnO4 were run from the burette into the conical flask. ………………… mol of KMnO4 were run from the burette into the conical flask. Put the correct number of electrons into each of the following half-equations to balance the electrical charges. MnO4 – + 8H+ + ……… e– Mn2+ + 4H2O C2O2– 4 2CO2 + ……… e– Calculate how many moles of ethanedioate ions, C2O2– 4 , reacted with the KMnO4 run from the burette. ………………… mol of ethanedioate ions reacted with the KMnO4 run from the burette. Calculate the concentration, in mol dm–3, of C2O2– 4 in FB 3. The concentration of C2O2– 4 in FB 3 is ………………… mol dm–3. Calculate the concentration, in mol dm–3, of C2O2– 4 in FB 2. The concentration of C2O2– 4 in FB 2 is ………………… mol dm–3. i ii iii iv v

4 9701/32/M/J/09 © UCLES 2009 For Examiner’s Use Calculate the concentration, in g dm–3, of H2C2O4.2H2O in FB 2. [Ar: H, 1.0; C, 12.0; O, 16.0] FB 2 contains ………………… g dm–3 H2C2O4.2H2O. [5] [Total: 12] 2 You are provided with the following. FB 4, anhydrous sodium carbonate, Na2CO3 FB 5, solid sodium hydrogencarbonate, NaHCO3 3.0 mol dm–3 hydrochloric acid You are to determine the enthalpy change of reaction,
H, for the following reactions. Na2CO3(s) + 2HCl (aq) 2NaCl (aq) + CO2(g) + H2O(l)
H1 NaHCO3(s) + HCl (aq) NaCl (aq) + CO2(g) + H2O(l)
H2 (a) Reaction of FB 4, Na2CO3, with an excess of 3.0 mol dm–3 hydrochloric acid Read through the following instructions carefully before starting the experimental work. • Support the plastic cup in the 250 cm3 beaker provided. • Use the measuring cylinder to transfer 50 cm3 of 3.0 mol dm–3 hydrochloric acid into the plastic cup. • Weigh the tube containing FB 4, anhydrous sodium carbonate. • Measure and record the steady temperature of the acid in the beaker. • Add the contents of the tube to the acid in three separate lots, taking care that the mixture does not overflow. • Stir and record the highest temperature obtained. • Reweigh the tube containing residual FB 4. Record in an appropriate form below all of your weighings and temperature measurements together with the mass, m1, of FB 4 added and the temperature rise,
T1. [1]

5 9701/32/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (b) Calculate the temperature rise per gram of FB 4, Na2CO3, used in the experiment.
T1 m1 = … °C g–1 [2] (c) Calculate the enthalpy change,
H1, for the following reaction. Na2CO3(s) + 2HCl (aq) 2NaCl (aq) + CO2(g) + H2O(l)
H1 = – (22.79 ×
T1 m1 ) kJ mol–1
H1 = – … kJ mol–1 (d) Reaction of FB 5, NaHCO3, with an excess of 3.0 mol dm–3 hydrochloric acid 50 cm3 of 3.0 mol dm–3 hydrochloric acid contains 0.15 mol HCl. Calculate the mass of NaHCO3 that will react with 0.15 mol HCl. [Ar: C, 12.0; H, 1.0; O, 16.0; Na, 23.0] [1] The reaction of NaHCO3(s) and HCl (aq) is endothermic. The expected fall in temperature when 1.0 g NaHCO3(s) is added to 50 cm3, an excess, of 3.0 mol dm–3 HCl is approximately 1.5 °C. (e) The error in reading a –10 °C to +110 °C thermometer is ±0.5 °C. What is the maximum error when using two temperature measurements to calculate a temperature change? The maximum error is ± … °C. [1] (f) Determine the maximum percentage error in the calculated temperature change when 1.0 g of NaHCO3 is added to 50 cm3 of 3.0 mol dm–3 hydrochloric acid. The maximum error is ± … %. [1]

6 9701/32/M/J/09 © UCLES 2009 For Examiner’s Use (g) Use your answer to (d) and the expected temperature change of −1.5 °C g–1 to select a mass of FB 5, NaHCO3, to use in an experiment with 50 cm3 of 3.0 mol dm–3 hydrochloric acid. The mass selected should give an appropriate, measurable, temperature fall. Note: The hydrochloric acid should be in excess and the percentage error in temperature measurement should be kept to a minimum. Mass of FB 5 to be used = … g. Predicted temperature fall = … °C. [1] (h) Read through the instructions before starting any practical work. • Empty, rinse, and shake dry the plastic cup used in (a). • Support the plastic cup in the 250 cm3 beaker provided. • Use the measuring cylinder to transfer 50 cm3 of 3.0 mol dm–3 hydrochloric acid into the plastic cup. • Weigh the empty tube labelled NaHCO3. • Add the mass of FB 5 you have selected in (g) to the tube and reweigh. • Measure and record the steady temperature of the acid in the beaker. • Add the contents of the tube to the acid in three separate lots, taking care that the mixture does not overflow. • Stir and record the lowest temperature obtained. • Reweigh the tube containing residual FB 5. Record in an appropriate form below all of your weighings and temperature measurements together with the mass, m2, of FB 5 added and the temperature fall,
T2. [2] (i) Calculate the temperature fall per gram of FB 5, NaHCO3, used in the experiment.
T2 m2 = … °C g–1 [3]

7 9701/32/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (j) Calculate the enthalpy change,
H2, for the following reaction. NaHCO3(s) + HCl (aq) NaCl (aq) + CO2(g) + H2O(l)
H2 = + (18.06 ×
T2 m2 ) kJ mol–1
H2 = + … kJ mol–1 (k) It is not possible to measure experimentally the enthalpy change,
H3, for the following reaction as it does not take place in the laboratory. Na2CO3(s) + CO2(g) + H2O(l) 2NaHCO3(s) It is possible, however, to calculate a “theoretical” value of
H3 for this reaction from the results of the experiments you have carried out and a Hess cycle. 2HCl (aq) + Na2CO3(s) + H2O(l) + CO2(g)
H3 2NaHCO3(s) + 2HCl (aq)
H1 2
H2 2NaCl (aq) + 2CO2(g) + 2H2O(l) Derive an equation to link
H1,
H2, and
H3. Use your equation and the results from (c) and (j) to calculate a value for
H3.
H3 = … kJ mol–1 [2] (l) Suggest a modification to the experimental method in order to reduce the transfer of heat energy to or from the contents of the plastic cup during the experiment. … … [1] [Total: 15]

8 9701/32/M/J/09 © UCLES 2009 For Examiner’s Use 3 FB 6 and FB 7 each contain one of the following sodium halides, NaCl, NaBr, NaI. (a) Place half of the solid FB 6 provided in a test-tube. Half fill the test-tube with distilled water and shake to dissolve the solid. Label the tube FB 6. Do the same with FB 7, labelling the tube FB 7. Keep the remaining solid for (c). (b) You are to select appropriate reagents from those provided and to perform tests to identify which halide ion is present in FB 6 and which in FB 7. Retain some of the FB 7 solution for test (d). In an appropriate form below record the tests performed and the results of those tests. From the recorded observations the following halides are identified. FB 6 contains … FB 7 contains … [4] (c) Carry out the following tests. [Care: unpleasant fumes may be produced] test observations FB 6 FB 7 Place the remaining solid in a clean, dry test-tube and add 5 drops of concentrated sulfuric acid (care: the concentrated acid is very corrosive), then as soon as you have made your observation, half fill the test-tube with distilled water to dissolve the remaining solid and any fumes produced. Transfer 1 cm depth of the resulting solution to a test-tube and add a few drops of starch solution. [2] i ii iii iv

9 9701/32/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (d) Carry out the following tests. test observations Place 1 cm depth of the solution of FB 7 prepared in (a) in a test-tube. Add 1 cm depth of aqueous bromine, [Care: unpleasant fumes] then, add a few drops of starch solution. [1] (e) Use your observations and knowledge of halogen chemistry to explain the reactions in (c) and identify the chemical behaviour of the concentrated sulfuric acid in the reaction. … … … … Use your observations and knowledge of halogen chemistry to explain what happens when the solutions are mixed in (d). … … … … [3]

10 9701/32/M/J/09 © UCLES 2009 For Examiner’s Use (f) FB 8 and FB 9 each contain one cation from those listed on page 11. Carry out the following tests to identify the cation present in each solution. test observations FB 8 FB 9 To 1 cm depth of solution in a test-tube, add aqueous sodium hydroxide a little at a time then, add an excess of the reagent to give no more than 4 cm depth of solution in the test-tube. To 1 cm depth of solution in a test-tube, add aqueous ammonia a little at a time then, add an excess of the reagent to give no more than 4 cm depth of solution in the test-tube. The cation present in FB 8 is … The cation present in FB 9 is … [3] [Total: 13]

11 9701/32/M/J/09 © UCLES 2009 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, NH+ 4 (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 9701/32/M/J/09 © UCLES 2009 2 Reactions of anions ion reaction carbonate, CO2– 3 CO2 liberated by dilute acids chromate(VI), CrO2– 4 (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, NO– 3(aq) NH3 liberated on heating with OH–(aq) and Al foil nitrite, NO– 2(aq) NH3 liberated on heating with OH–(aq) and Al foil, NO liberated by dilute acids (colourless NO (pale) brown NO2 in air) sulfate, SO2– 4 (aq) gives white ppt. with Ba2+(aq) (insoluble in excess dilute strong acid) gives white ppt. with Pb2+(aq) sulfite, SO2– 3 (aq) SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid) 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 aqueous acidified potassium dichromate(VI) (aq) from orange to green 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2009 question paper for the guidance of teachers 9701 CHEMISTRY 9701/32 Paper 32 (Advanced Practical Skills 2), 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 must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2009 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 Question 1 Supervisor’s Report Calculate, correct to 2 d.p., the titre if the Supervisor had diluted 42.75 cm3 of FB 2. This is given by the expression titre diluted volume 42.75 × Candidate scripts Calculate the scaled titre for 42.75 cm3 of FB 2. Record the scaled value against the titration table and calculate the difference to Supervisor. Question Sections Indicative material Mark 1 (a) PDO Layout (i) Tabulates initial and final burette readings and volume added in each of the tables. Do not award this mark if any final and initial burette readings are inverted or 50 is used as the initial burette reading. 1 PDO Recording (ii) Both burette readings in the dilution table and final and initial burette readings for all accurate titres in the titration table recorded to the nearest 0.05 cm3. 1 MMO Collection (iii) Follows instructions: dilutes 42.50 cm3 to 43.00 cm3 and has any two titres, which may include a rough titre, within 0.20 cm3 1 MMO Decisions (iv) Has at least two titres within 0.1 cm3. Do not include any titre labelled “rough”/”trial” unless the candidate has ticked that value or used it in an expression when calculating the average in (b). 1 (v) and (vi) Accuracy Give (v) and (vi) if difference to Supervisor is 0.3 or less Give (vi) only for a difference of 0.3+ to 0.5 Give neither for a difference greater than 0.5 2 [6]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 (b) ACE Interpretation Working must be shown in this section or the selected titres ticked in the titration table Candidate selects/calculates appropriate “average” from any titre values within 0.20 cm3. Candidate is permitted to use a titre labelled “rough” or “trial”. Where all titres are given to 1 decimal place the average should be calculated correct to 1 or 2 decimal places. Where any titre is recorded to 2 decimal places, the average should be calculated to 2 decimal places or rounded to the nearest 0.05 cm3. 1 [1] (c) ACE Interpretation PDO Display (i), (ii) and (iii) Check each step of the calculation. Award three marks if all steps are chemically correct, ignore evaluation errors. Withhold 1 mark for each chemical error – no negative marks. (Count non-completed steps as chemical errors.) step 1 0.023 1000 titre × step 2 5 e– in 1st eqn; 2 e– in 2nd eqn step 3 × candidate’s ratio from step 2 The expected ratio is 5/2 step 4 × 25 1000 step 5 × diluted volume 250 [or (10 × step 3) × diluted volume 1000 ] step 6 × 126 (iv) Working shown in at least three of steps 1 & 3–6. (v) Answers to 3 or 4 significant figures in final answer to each step attempted from steps 1 & 3–6 (minimum of three steps required). 3 1 1 [5] [Total: 12]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 Question 2 Round all thermometer readings to the nearest 0.5 °C Supervisor’s Report Calculate ∆T/m correct to 2 d.p. for each experiment. Candidate’s scripts Calculate ∆T/m correct to 2 d.p. for each experiment. Record values of ∆T/m on script and use in assessing accuracy marks. Where a candidate has performed one or both of the experiments a number of times (as distinct from adding in portions and recording the increasing temperature on each addition): Calculate (unrounded) the ∆T/m value for each experiment, then Take the average of the closest pair, rounded to 2 d.p. Question Sections Indicative material Mark 2 (a) PDO Layout Tabulates or lists all experimental readings: • mass of tube + FB 4 • mass of tube + residue • mass, m1, of FB 4 • initial temperature • final temperature • ∆T 1 [1] (b) MMO Quality Calculate the difference between the Supervisor and candidate values of ∆T/m. Give two marks for a difference up to 0.1 °C g–1 Give one of these two marks for a difference of +0.1 °C g–1 to 0.3 °C g–1. 2 [2] (c) No mark (d) ACE Interpretation Calculates (0.15 × 84) or has 12.6 g NaHCO3 1 [1] (e) ACE Interpretation Gives the maximum error as 1.0 °C. Do not award this mark for an answer of 1. 1 [1] (f) ACE Interpretation Calculates 50 . 1 (e) to answer candidates × 100% correct to: 2 significant figures (67%) or 3 significant figures (66.7%) or 4 significant figures (66.67%) Accept 662/3. 1 [1] (g) MMO Decisions Selects a mass between 8.0 and < mass of NaHCO3 calculated in (d). (If the candidate’s answer to (d) is < 8.0 g; the mass selected should be in the range: 2/3 × mass in (d) and < mass in (d) ) and estimates (mass × 1.5) correctly If no mass has been calculated/given in (d), this mark cannot be awarded. 1 [1]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 (h) PDO recording Records all weighings, consistently, to at least 1 decimal place in (a) and (h). Records all thermometer readings to (.0) or (.5) in (a) and (h). Where the experiment in (h) has not been attempted, only the mark for consistent weighings may be awarded – from the experimental results in (a). 1 1 [2] (i) MMO Collection Where mass of (empty) test-tube and mass of test- tube + FB 5 are given: mass added to the test-tube should be ±0.2 g from mass selected in (g). If no mass of (empty) test-tube is recorded, but mass of test-tube + FB 5 and mass of test-tube + residual FB 5 are recorded: mass of FB 5 used in the experiment should be in the range (+0.2 to –0.5)g of mass selected in (g). Calculate the difference between 1.30 and the candidate’s value of ∆T/m. Give two marks for a difference up to 0.2 °C g–1 Give one of these two marks for a difference of +0.2 °C g–1 to 0.4 °C g–1 1 2 [3] (k) ACE Conclusions ACE Interpretation Manipulates Hess cycle to show that ∆H3 = ∆H1 – 2∆H2 or ∆H1 = ∆H3 + 2∆H2 or 2∆H2 = ∆H1 – ∆H3 Correctly calculates a value for ∆H3 from equation given by candidate and candidate values from (c) and (j). A +ve sign must be given for any endothermic change The candidate must use the exact values given in the final answers to (c) and ∆T/m but may then correctly round their answer to at least 3 significant figures. 1 1 [2] (l) ACE Improvement Suggests additional insulation (lid etc.) Candidate must suggest a suitable material to use as insulation or explain how or where the insulation is to be applied. or plots cooling/heating curves, extrapolating to lowest/highest temperature. 1 [1] [Total: 15]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 Question Sections Indicative material Mark FB 6 is NaBr; FB 7 is NaI; FB 8 is ZnSO4(aq), FB 9 is MgSO4(aq) 3 (a) No mark Reagents available:HCl; NaOH(aq); NH3(aq); BaCl2/Ba(NO3)2(aq); Pb(NO3)2(aq); AgNO3(aq); K2Cr2O7(aq); Br2(aq); concentrated H2SO4 (b) MMO Decisions (i) Selects AgNO3 as one reagent and NH3(aq) added to the ppt produced with AgNO3 or Pb(NO3)2 / K2Cr2O7 added as fresh reagents. The reagent must be named or the formula of the reagent given. 1 MMO Collection (ii) Correct observations for an appropriate pair of reagents for FB 6 1 ACE Conclusion (iii) Correct observations for an appropriate pair of reagents for FB 7 Expected observations: FB 6 (Br –) FB 7 (I –) AgNO3 cream ppt (off-white ppt is NOT acceptable) yellow ppt NH3(aq) ppt insoluble or partially soluble ppt insoluble Pb(NO3)2 white ppt yellow ppt K2Cr2O7 no change brown solution One of the observation marks can be awarded for correct observations on adding AgNO3 to FB 6 and FB 7 if this is to the candidate’s advantage. (iv) Makes appropriate consequential conclusions from observations given (FB 6 contains Br– and FB 7 contains I– but Cl – may be given from white ppt with Ag+. Allow Br– from off-white ppt insoluble or partially soluble in ammonia. 1 1 [4]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 (c) MMO Collection Look for the following marking points: FB 6 FB 7 (i) yellow/orange/red solid, solution, liquid or mixture (not colour alone) or orange/red/brown gas or vapour (i) brown/grey/black (not blue-black) solid or purple gas/vapour (gas can be awarded in either of the first two boxes) (ii) white or steamy fumes (in either of the first two boxes) (ii) “bad-egg” smell or (smell of) H2S or test for H2S (including dichromate turning green) (iii) positive test for SO2 (iii) Orange/dark red/red-brown/ brown solution (no solid) on adding distilled water (iv) no change (but not no ppt) with starch (iv) blue/blue-black/ purple/purple- black/black colour (of solution or solid) Give one mark for two out of four correct marking points for FB 6 Give one mark for three out of four correct marking points for FB 7 1 1 [2] (d) MMO Collection Observes: yellow/orange/red/brown colour on adding Br2(aq), providing there is no precipitate or solid and blue/blue-black/purple/purple-black/black colour (of solution or solid) 1 [1] (e) ACE Conclusions Conclusions for halide/sulfuric acid reaction Any reference to Br2 or I2 being produced or halide oxidised Sulfuric acid is an oxidising agent. H2SO4 oxidises halide scores both marks. Conclusions for bromine water/iodide reaction Correct description of displacement or redox reaction involving both of the halogens/halides: e.g. (i) halogen/halide Bromine oxidises iodide ions. (ii) halogen/halogen Br2 displaces I2. Iodine is displaced by bromine. There is no suitable statement linking halide and halide. 1 1 1 [3]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9701 32 © UCLES 2009 (f) MMO Collection ACE Conclusions FB 8 Observes white ppt soluble/dissolving/disappearing (in excess) for each reagent. FB 9 Observes white ppt insoluble/not dissolving/remaining (in excess) for each reagent Mark consequentially on observations involving white precipitates only. Expected ions are Zn2+ in FB 8 and Mg2+ in FB 9 Symbol and ion charge must be correct in any deduction or the name of the ion given: e.g. Zn2+ or zinc but not Zn 1 1 1 [3] [Total: 13]