Cambridge A Level Chemistry 9701 — 2006 Oct/Nov Paper 3 · Variant 1

This document consists of 8 printed pages. SP (NF) T20258/3 © UCLES 2006 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level CHEMISTRY 9701/03 Paper 3 Practical Test October/November 2006 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Instructions to Supervisors. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name, including practical session and laboratory where appropriate, in the spaces 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. Answer all questions. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are provided on pages 7 and 8. At the end of the examination, fasten your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Centre Number Candidate Number Name For Examiner’s Use 1 2 Total Session Laboratory

2 9701/03/O/N/06 For Examiner’s Use © UCLES 2006 1 FA 1 is an aqueous solution of hydrochloric acid, HCl. FA 2 is aqueous potassium iodate(V) containing 4.93 g dm–3 of KIO3. FA 3 is aqueous potassium iodide, KI. FA 4 is aqueous sodium thiosulphate, Na2S2O3. In the presence of acid, iodate(V) ions react with iodide ions to form iodine and water. IO3 –(aq) + 5I–(aq) + 6H+(aq) 3I2(aq) + 3H2O(l) If sodium thiosulphate is present in the reaction mixture the iodine formed is immediately reduced back to iodide and the solution remains colourless. Iodate(V) ions can therefore be titrated against acid in the presence of an excess of iodide and thiosulphate ions. You are to use this method to determine the concentration of the hydrochloric acid, FA 1. (a) Dilution of FA 1 Using a burette, run between 34.00 cm3 and 35.00 cm3 of FA 1 into the 250 cm3 graduated flask, labelled FA 5. Record the burette readings in Table 1.1. Table 1.1 Dilution of FA 1 final burette reading / cm3 initial burette reading / cm3 volume of FA 1 run into the flask / cm3 Make the solution up to 250 cm3 with distilled water and mix thoroughly. Fill a second burette with this diluted acid, FA 5. (b) Titration of IO3 – with H+ in FA 5 Pipette 25.0 cm3 of FA 2 into a conical flask and use a measuring cylinder to add to the flask 10 cm3 of FA 3 and 25 cm3 of FA 4. Add five drops of bromophenol blue indicator and titrate with FA 5 until the end-point is reached. The colour of bromophenol blue changes to yellow at the end-point. Record your titration results in Table 1.2. Repeat the titration as many times as you think necessary to obtain accurate results. Make certain that the recorded results show the precision of your practical work. Table 1.2 Titration of FA 2 with FA 5 final burette reading / cm3 initial burette reading / cm3 volume of FA 5 used / cm3 [8] Summary 25.0 cm3 of FA 2 reacted with … cm3 of FA 5. Show which results you used to obtain this volume of FA 5 by placing a tick (✓) under the readings in Table 1.2.

3 9701/03/O/N/06 [Turn over For Examiner’s Use © UCLES 2006 You are advised to show full working in all parts of the calculations. (c) Calculate how many moles of potassium iodate(V), KIO3, were pipetted into the conical flask. [Ar: K, 39.1; I, 127.0; O, 16.0] [2] (d) Calculate how many moles of hydrogen ions, H+, reacted with the iodate(V) ions in the flask during the titration. IO3 –(aq) + 5I–(aq) + 6H+(aq) 3I2(aq) + 3H2O(l) [1] (e) Calculate the concentration, in mol dm–3, of hydrogen ions in FA 5. [1] (f) Calculate the concentration, in g dm–3, of hydrochloric acid in FA 1. [Ar: H, 1.0; Cl, 35.5] [3] [Total: 15]

4 9701/03/O/N/06 For Examiner’s Use © UCLES 2006 2 FA 6 is a mixture of two solids provided in a stoppered boiling tube. One of the solids, FA 7 is soluble in water; the other, FA 8 is insoluble in water. Each solid contains one cation and one anion from the ions listed on pages 7 and 8. In all tests, the reagent should be added gradually with shaking after each addition. Record your observations in the spaces provided. Your answers should include • details of colour changes, precipitates formed and the solubility of any precipitate when an excess of the reagent is added, • details of the test used to identify any gases given off in the reaction. You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional or confirmatory tests for ions present should be attempted. Candidates are reminded that definite deductions may be made from tests where there appears to be no reaction. test observations [3] (a) Add water to the boiling-tube labelled FA 6 until it is about half-full. Stopper and shake the tube for 1 minute. Filter the mixture and retain both filtrate and residue for further tests. Tests on the filtrate which contains FA 7 (b) To 1 cm depth of the filtrate from (a), in a boiling-tube, add 2 cm depth of aqueous sodium hydroxide. Gently warm the solution. Take care as a solution containing sodium hydroxide may ‘bump’ on heating and eject hot corrosive sodium hydroxide. (c) To 1 cm depth of the filtrate from (a), in a boiling-tube, add 1 cm depth of aqueous lead(II) nitrate; then heat the mixture to boiling point; then cool the tube by standing in a beaker of cold water.

5 9701/03/O/N/06 [Turn over For Examiner’s Use © UCLES 2006 test observations (d) To 1 cm depth of the filtrate from (a), in a test-tube, add 5 drops of aqueous silver nitrate; then add 5 cm depth of dilute aqueous ammonia. Use the information in the Qualitative Analysis Notes on pages 7 and 8 to identify the ions present in FA 7. The cation present in FA 7 is … Which observations indicate the cation you have selected? … … … [1] The anion present in FA 7 is … Which observations indicate the anion you have selected? … … … [1]

6 9701/03/O/N/06 For Examiner’s Use © UCLES 2006 Tests on the residue which contains FA 8 test observations [3] (e) Transfer the residue to a boiling-tube and add 4 cm depth of dilute hydrochloric acid. Filter the mixture and retain the filtrate. (f) To 1 cm depth of the filtrate from (e) in a test-tube add, a little at a time, 5 cm depth of aqueous sodium hydroxide. (g) To 1 cm depth of the filtrate from (e) in a test-tube add, a little at a time, 5 cm depth of dilute aqueous ammonia. Use the information in the Qualitative Analysis Notes on pages 7 and 8 to identify the ions present in FA 8. The cation present in FA 8 is … Which observations indicate the cation you have selected? … … … [1] The anion present in FA 8 is … Which observations indicate the anion you have selected? … … … [1] [Total: 10]

7 9701/03/O/N/06 © UCLES 2006 [Turn over 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) 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. insoluble in excess green ppt. 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. insoluble in excess off-white ppt. 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.]

8 9701/03/O/N/06 © UCLES 2006 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) sulphate, SO4 2– (aq) gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid) sulphite, SO3 2– (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, Cl2 bleaches damp litmus paper hydrogen, H2 ‘pops’ with a lighted splint oxygen, O2 relights a glowing splint sulphur dioxide, SO2 turns 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 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 October/November 2006 question paper 9701 CHEMISTRY 9701/03 Paper 3 (Practical Test), maximum raw mark 25 This mark scheme is published as an aid to teachers and students, 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. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the report on the examination. The grade thresholds for various grades are published in the report on the examination for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2006 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 1 Mark Scheme Syllabus Paper GCE A LEVEL – Oct/Nov 2006 9701 3 © UCLES 2006 Question 1 (b) Candidate’s results Check (and correct if necessary) all subtractions in Tables 1.1 and 1.2. The subtraction of titration results labelled as rough need not be checked unless the candidate has included them in the volumes used to calculate the average. Tick (if accepting the candidate’s value) or correct this value, recording it by titration Table 1.2 on the script. Calculate for each candidate: diluted 1 FA of volume s ' Supervisor diluted 1 FA of volume s Candidate' x Titre s Candidate' . Record this titre, correct to two decimal places, against Table 1.2 and calculate the difference between the calculated value and the Supervisor’s titre. Award accuracy marks on the difference as shown on the next page.

Page 2 Mark Scheme Syllabus Paper GCE A LEVEL – Oct/Nov 2006 9701 3 © UCLES 2006 Award accuracy marks for differences as follows: Accuracy mark Spread Penalty Mark Difference to Supervisor / cm3 Range used / cm3 Deduction 8 Up to 0.20 0.20+ to 0.25 1 7 0.20+ to 0.25 0.25 to 0.30 2 6 0.25+ to 0.30 0.30+ to 0.35 3 5 0.30+ to 0.40 0.35+ to 0.40 4 4 0.40+ to 0.60 0.40+ to 0.50 5 3 0.60+ to 0.80 0.50+ to 0.60 6 2 0.80+ to 1.00 0.60+ to 0.80 7 1 1.00+ to 1.50 Greater than 0.80 8 0 Greater than 1.50 [8] Deduct from the accuracy mark one mark for each of the following errors: (i) Volume diluted, as recorded by the candidate in the final line of Table 1.1 is outside of the range 34.00 cm3 to 35.00 cm3. Ignore any subtraction error that would take the volume out of range (ii) Any Initial and Final Burette reading transposed or 50 used as initial burette reading in either table or Final burette readings in either table (except for any titration recorded as Rough) not recorded to 2 decimal places, or ”impossible” burette readings (e.g. 23.47 cm3) recorded at any point in either of the tables. All final burette readings = 50 cm3. (When assessing titration volumes to use you will need to consider this case carefully. Is there a general inversion of initial and final burette readings with 50 used instead of 0 or is this a genuine claim that all titres finished on 50 cm3. The volume run out will be the best evidence to use) (iii) No two recorded (uncorrected) titres within 0.1 cm3 in Table 1.2. (iv) An incorrect average calculated or No selection of at least two titres for the calculation of the average shown (selected titres may be ticked or used in a calculation of the average.) or Error in subtraction in any accurate titre (any rough titre if included in selection of titres to calculate the average) or error in subtraction in Table 1.1 THERE IS A MAXIMUM DEDUCTION OF TWO MARKS FROM THE ACCURACY MARKS

Page 3 Mark Scheme Syllabus Paper GCE A LEVEL – Oct/Nov 2006 9701 3 © UCLES 2006 (c) Give one mark for calculating the correct concentration in mol dm-3 1 . 214 93 . 4 or 0.023(0) Do not give this mark if K = 39.0 has been used. Give one mark for candidate by calculated dm mol in ion concentrat x 1000 25 3 - or Give one mark for 25 x 1000 93 . 4 and one mark for this expression 214.1 1 x (one) (one) The answer 5.75(7) x 10-4 with no working gains both marks [2] (d) Give one mark for 6 x (c) ans or 3.45(4) x 10-3 [1] (e) Give one mark for Titre s Candidate' 1000 x (d) ans [1] (f) Give two marks for 36.5 x diluted 1 FA of volume s Candidate' 250 x (e) ans one one Give one of these two marks for any answer where only (e) x 36.5 is seen. and Give one mark for a fully correct answer within 1% of the value calculated by the examiner. Do not give this mark if there are ‘chemical’ errors in (c) to (f) even if these errors are self-cancelling. The mark may be given if 214 rather than 214.1 has been used for Mr of KIO3, providing the final answer is within 1% of the examiner calculated value The correct answer is: diluted 1 FA of volume s Candidate' X Titre s Candidate' 31517.69 [3] [Total for Qn 1 15] 5.75(7) x 10-4 3.45(4) x 10-3 0.138 1.001 36.54 If 34.5 cm3 of FA 1 are diluted, the expected titre is around 25 cm3. Evaluations for these values are given, in boxes, as a guide to expected values

Page 4 Mark Scheme Syllabus Paper GCE A LEVEL – Oct/Nov 2006 9701 3 © UCLES 2006 2 FA 6 is a mixture of soluble FA 7 (ammonium chloride) and insoluble FA 8 (manganese(II) carbonate) Some centres were unable to obtain manganese(II) carbonate and have been instructed to use magnesium zinc or copper carbonate. Magnesium carbonate was the recommended choice. RETROSPECTIVE OBSERVATION MARKS MAY BE EARNED FROM THE CONCLUSIONS WHERE INCOMPLETE INFORMATION RECORDED, IN THE OBSERVATION BOX, AGAINST THE TEST IS COMPLETED. DO NOT GIVE RETROSPECTIVE MARKS FOR CONTRARY INFORMATION Tests on the Filtrate FA 7 Test Observations (b) To 1 cm depth of the filtrate from (a) in a boiling-tube, add 2 cm depth of aqueous sodium hydroxide. Give one mark for No ppt. / colourless solution / no reaction (allow slightly brown – as MnCO3 might not be fresh) No yellow or orange colours 1 Gently warm the solution. Take care as a solution containing sodium hydroxide may ‘bump’ on heating and eject hot corrosive sodium hydroxide. Give one mark for Gas evolved – turns red litmus blue (or other appropriate test for ammonia gas) Ignore any precipitate in this section 1 (c) To 1 cm depth of the filtrate from (a) in a test-tube, add 1 cm depth of aqueous lead nitrate, then Give one mark for White precipitate which is heat the mixture to boiling point, then soluble/partially soluble in hot water 1 cool the tube by standing in a beaker of cold water Give one mark if the (white) precipitate reforms or crystals form 1 (d) To 1 cm depth of the filtrate from (a) in a test-tube, add 1 cm depth of aqueous silver nitrate. Give one mark for White precipitate ………………….. Then add 5 cm depth of dilute aqueous ammonia. Soluble in aqueous ammonia 1 TO GAIN ANY DEDUCTION MARK THERE MUST BE REFERENCE TO THE REAGENTS. REFERENCE TO THE TEST ALONE IS SUFFICIENT PROVIDING THE OBSERVATION MARK HAS BEEN GIVEN FOR THAT TEST. Give one mark if the cation in FA 7 is identified as NH4 + or ammonium and there is reference to ammonia evolved / alkaline gas / gas turning red litmus blue (on heating with sodium hydroxide.) There must be a clear or unambiguous link to test (b) part (ii). [1] Give one mark if the anion is identified as Cl - and There is reference to white precipitate with Pb2+ or white ppt, soluble in ammonia with Ag+. [1]

Page 5 Mark Scheme Syllabus Paper GCE A LEVEL – Oct/Nov 2006 9701 3 © UCLES 2006 Tests on the residue FA 8 Test Observations [3] (e) Transfer the residue to a boiling-tube and add 4 cm depth of dilute hydrochloric acid. Retain the solution for tests (f) and (g). Give one mark for Gas evolved turns lime-water milky / cloudy / chalky or gives a white ppt with Ca(OH)2 Details of the test may be given in the conclusion 1 (f) To 1 cm depth of the solution from (e) in a test-tube add, a little at a time, 5 cm depth of aqueous sodium hydroxide. Give one mark for Off-white / buff / pale-brown ppt. Insoluble in excess (NaOH) [For Mg2+ - white ppt insol in excess For Zn2+ - white ppt sol in excess For Cu2+ - blue ppt insol in excess] 1 (g) To 1 cm depth of the solution from (e) in a test-tube add, a little at a time, 5 cm depth of dilute aqueous ammonia. Give one mark for Off-white / buff / pale-brown ppt. Insoluble in excess (NH3(aq)) [For Mg2+ - white ppt insol in excess For Zn2+ - white ppt sol in excess For Cu2+ - pale blue ppt sol in excess or blue ppt sol in excess to form a deep blue soln] 1 Give one mark if the cation in FA 8 is identified as Mn2+ or manganese(II) [Mg2+, Zn2+, Cu2+] and There is reference to the colour of the precipitate and insolubility of precipitate in excess of sodium hydroxide and aqueous ammonia or reference to an off-white precipitate in each test. [1] Allow deductions of other cations, given from incorrect observations, providing all observations – including the solubility of any precipitate in excess NaOH and ammonia for the ion given. e.g. deduction of Fe3+ from brown or red-brown precipitate, insoluble in excess aqueous NaOH and ammonia. Give one mark if the anion is identified as CO3 2- or carbonate and there is reference to effervescence with hydrochloric acid or [1] carbon dioxide is named (without a confirmatory test) as the gas given off and effervescence is an observation in (e) or there is reference back to a positive test for carbon dioxide in (e). There are 12 scoring points. If a candidate scores in excess of 10 points record the raw score, crossed through and replaced by 10 max. [Total for Qn 2 10] [Total for Paper 25]