Cambridge A Level Chemistry 9701 — 2005 Oct/Nov Paper 3 · Variant 1

This document consists of 7 printed pages and 1 blank page. SP (SJF3515) S81618/4 © UCLES 2005 [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 2005 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 details, including practical session and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen in the spaces provided on the Question Paper. 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. The number of marks is given in brackets [ ] at the end of each question or part question. You are advised to show all working in calculations. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 6 and 7. Centre Number Candidate Number Name For Examiner’s Use 1 2 TOTAL SESSION LABORATORY

© UCLES 2005 2 9701/03/O/N/05 For Examiner's Use 1 FA 1 is an aqueous solution containing 38.10 g dm–3 of borax crystals. Borax is disodium tetraborate-x-water, Na2B4O7.xH2O. FA 2 is 1.00 mol dm–3 HCl. You are required to find the number of moles of water of crystallisation, x, in the borax crystals. Disodium tetraborate reacts with hydrochloric acid according to the equation below. Na2B4O7(aq) + 2HCl(aq) + 5H2O(l) →2NaCl(aq) + 4H3BO3(aq) (a) Use a burette to measure between 44.50 cm3 and 45.50 cm3 of FA 2 into the 250cm3 volumetric (graduated) flask labelled FA 3. Record your burette readings in Table 1.1. Table 1.1 Dilution of FA 2 Fill the flask to the 250 cm3 mark with distilled or deionised water and mix the contents thoroughly by shaking. This solution is FA 3. Fill the second burette with the diluted hydrochloric acid, FA 3. (b) Pipette 25.0 cm3 of FA 1 into a conical flask and add a few drops of the indicator provided. Titrate the contents of the conical flask with FA 3 until the appropriate colour change is observed at the end-point. 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 1 with FA 3 The indicator used was … Summary 25.0 cm3 of FA 1 reacted with ………………. cm3 of FA 3. Show which results you used to obtain this volume of FA 3 by placing a tick (✓) under the readings in Table 1.2. [6] final burette reading / cm3 initial burette reading / cm3 volume of FA 3 used / cm3 final burette reading / cm3 initial burette reading / cm3 volume of FA 2 used / cm3

You are advised to show full working in all parts of the calculations. (c) Calculate the concentration, in mol dm–3, of hydrochloric acid in the diluted solution FA 3. [1] (d) Calculate how many moles of hydrochloric acid were run from the burette into the conical flask during the titration of FA 1 with FA 3. [1] (e) Calculate the concentration, in mol dm–3, of the disodium tetraborate in FA 1. Na2B4O7(aq) + 2HCl(aq) + 5H2O(l) →2NaCl(aq) + 4H3BO3(aq) [2] (f) Calculate the concentration, in g dm–3, of disodium tetraborate, Na2B4O7, in FA 1. [Ar: Na, 23.0; B, 10.8; O, 16.0.] [2] (g) FA 1 contains 38.10 g dm–3 of borax crystals, Na2B4O7.xH2O. Use this information and your answer to (f) to calculate the mass of water present in the dissolved crystals. [1] (h) Calculate the number of moles of water present in 38.10 g of borax crystals. Use this answer and the answer to (e) to calculate the value of x in Na2B4O7.xH2O. [2] [Total:15] 3 9701/03/O/N/05 [Turn over For Examiner's Use © UCLES 2005

2 FA 4 contains one cation from those listed on page 6. FA 4 also contains one anion but this is not an ion listed on page 7. In all tests, the reagent should be added gradually until no further change is observed, with shaking after each addition. Record your observations in the spaces provided. Your answers should include • details of colour changes and precipitates formed, • the names of gases evolved and details of the test used to identify each one. 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. 4 9701/03/O/N/05 For Examiner's Use © UCLES 2005 Test Observations [6] Candidates are reminded that definite deductions may be made from tests where there appears to be no reaction. (a) Transfer two thirds of the solid FA 4 to a boiling-tube and add about 7 cm depth of dilute nitric acid. Cautiously warm the tube until the orange colour of the solid is no longer visible. Filter the mixture and retain filtrate for further tests. Wash the residue with water and retain residue for further tests. (b) Transfer the remaining solid FA 4 to a hard glass test-tube and heat strongly. Identify, with a suitable test, the gas evolved. Tests on the filtrate (c) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous sodium hydroxide until there is no further change. (d) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous ammonia until there is no further change. By performing the tests below, you should be able to identify the cation and to draw a further conclusion as to the nature of FA 4.

(e) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous potassium iodide. Tests on residue (f) Cautiously place 1 cm depth of concentrated hydrochloric acid into a boiling-tube and add an equal volume of water. Add to the tube some of the residue from (a) and warm gently. Identify, with a suitable test, the gas evolved. Immediately the gas is identified rinse the contents of the tube into the sink. 5 9701/03/O/N/05 [Turn over For Examiner's Use © UCLES 2005 Test Observations Use the information in the Qualitative Analysis Tables on pages 6 and 7 to identify the cation present in FA 4. The cation present in FA 4 is … Give two pieces of evidence that support your choice of this ion. … … … [2] FA 4 behaves as … Give one piece of evidence that supports this behaviour. … … … … [2] [Total: 10]

QUALITATIVE ANALYSIS NOTES [Key: ppt. = precipitate] 1 Reactions of aqueous cations [Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.] 6 9701/03/O/N/05 © UCLES 2005 aluminium, Al 3+(aq) ammonium, NH4+(aq) barium, Ba2+(aq) calcium, Ca2+(aq) chromium(III), Cr3+(aq) zinc, Zn2+(aq) copper(II), Cu2+(aq) iron(II), Fe2+(aq) iron(III), Fe3+(aq) lead(II), Pb2+(aq) magnesium, Mg2+(aq) manganese(II), Mn2+(aq) reaction with NaOH(aq) NH3(aq) white ppt. soluble in excess ammonia produced on heating no ppt. (if reagents are pure) green ppt. insoluble in excess green ppt. insoluble in excess white ppt. with high [Ca2+ (aq)] pale blue ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution white ppt. soluble in excess white ppt. insoluble in excess white ppt. insoluble in excess white ppt. insoluble in excess white ppt. soluble in excess white ppt. soluble in excess grey-green ppt. soluble in excess giving dark green solution red-brown ppt. insoluble in excess off-white ppt. insoluble in excess off-white ppt. insoluble in excess white ppt. insoluble in excess no ppt. no ppt. grey-green ppt. insoluble in excess red-brown ppt. insoluble in excess ion

© UCLES 2005 2 Reactions of anions 3 Tests for gases 7 9701/03/O/N/05 carbonate, CO3 2– chromate(VI), CrO4 2–(aq) chloride, Cl–(aq) bromide, Br–(aq) iodide, I–(aq) nitrate, NO3 –(aq) nitrite, NO2 –(aq) sulphate, SO4 2–(aq) sulphite, SO3 2–(aq) ion reaction CO2 liberated by dilute acids yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) NH3 liberated on heating with OH–(aq) and Al foil, NO liberated by dilute acids (colourless NO →(pale) brown NO2 in air) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) NH3 liberated on heating with OH–(aq) and Al foil SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acid) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)); gives yellow ppt. with Pb2+(aq) gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acid) gas test and test result turns damp red litmus paper blue gives a white ppt. with limewater (ppt. dissolves with excess CO2) bleaches damp litmus paper ‘pops’ with a lighted splint relights a glowing splint turns potassium dichromate(VI) (aq) from orange to green ammonia, NH3 carbon dioxide, CO2 chlorine, Cl 2 hydrogen, H2 oxygen, O2 sulphur dioxide, SO2

BLANK PAGE 8 9701/03/O/N/05 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 and Advanced Level MARK SCHEME for the November 2005 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 initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. 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 minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 1 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9701 3 © University of Cambridge International Examinations 2005 Question 1 Supervisor’s results Check all subtractions in Tables 1.1 and 1.2. Select the titre average. Calculate, correct to 2 decimal places, the ratio: Volume of FA2 x Titre Record this value on the front of the Supervisor’s script and as a ringed value by Table 1.2 on each candidate script. Candidate’s results Check 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. Calculate, correct to 2 decimal places, Volume of FA 2 diluted x Titre Record this value by Table 1.2 on the script and calculate the difference to the Supervisor’s ratio. Award accuracy marks for differences as follows: Accuracy mark Spread Penalty Mark Difference to Supervisor Range used / cm3 Deduction 6 Up to 4.50 0.20+ to 0.25 1 5 4.50+ to 6.75 0.25 to 0.30 2 4 6.75+ to 9.00 0.30+ to 0.40 3 3 9.00+ to 13.50 0.40+ to 0.50 4 2 13.50+ to 18.00 0.50+ to 0.70 5 1 18.00+ to 22.50 Greater than 0.70 6 0 Greater than 22.50 6 Deduct from the accuracy mark one mark for each of the following errors: (i) Final burette readings in Tables 1.1 and 1.2 not recorded to 2 decimal places or in the wrong place in a Table, or “impossible” burette readings (e.g. 23.47 cm3) recorded at any point in the tables. (ii) No two recorded (uncorrected) titres within 0.1 cm3. (iii) An incorrect average calculated or no selection of at least two titres for the calculation of the average. Selected titres may be ticked or used in a calculation of the average. THERE IS A MAXIMUM DEDUCTION OF TWO MARKS FROM THE ACCURACY MARKS

Page 2 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9701 3 © University of Cambridge International Examinations 2005 In all calculations, ignore evaluation errors if working is shown. Where an answer is given with no working the Examiner is to check the appropriate working and the answer must be given correct for this working. (c) Give one mark for 1.00 x 250 diluted 2 FA of Volume 1 (d) Give one mark for 1000 Titre x (c) to answer 1 (e) Give two marks for 25 1000 x 2 1 x (d) to answer (one) (one) No marks are to be awarded if the answer to (d) has not been used unless the answer has been started again from first principles. 2 (f) Give one mark for answer to (e) x a clearly calculated M r (Mr does not have to be correct) and If full marks have been given in (c) to (e), give one mark for an answer within 1% of the answer calculated by the examiner from the candidate’s results. The correct answer is given by: Candidate’s Accuracy “product” x 1.6096 x 10-2 2 (g) Give one mark for (f) to answer - 10 . 38 1 (h) Give one mark for 18 (g) to answer and Give one mark for (e) to answer (h) of part first in calculated water of moles 2 Total for Question 1 = 15

Page 3 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9701 3 © University of Cambridge International Examinations 2005 Question 2 FA 4 is red lead oxide, Pb3O4. Test Observations [6] (a) Transfer half of the solid FA 4 provided to a boiling-tube and add about 7 cm depth of dilute nitric acid. Cautiously warm the tube until the orange solid is no longer visible. Filter the mixture and retain both filtrate and residue for further tests. Wash the residue with water. Give one mark for colourless filtrate and brown solid/precipitate/residue (b) Transfer the remaining FA 4 to a hard glass test-tube and heat strongly. Identify, with a suitable test, the gas evolved. Give one mark for identifying the gas as oxygen and giving an appropriate test, e.g. relights glowing splint/splint burns more brightly/splint glows more brightly Tests on the filtrate (c) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous sodium hydroxide until there is no further change. Give one mark for white precipitate soluble in excess sodium hydroxide (d) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous ammonia until there is no further change. Give one mark for white precipitate insoluble in excess ammonia (e) To 1 cm depth of the filtrate from (a) in a test-tube, add aqueous potassium iodide. Give one mark for yellow precipitate Tests on residue (f) Cautiously place 1 cm depth of concentrated hydrochloric acid into a boiling-tube and add an equal amount of water. Add to the tube some of the residue from (a) and warm gently. Identify, with a suitable test, the gas evolved. Immediately the gas is identified rinse the contents of the tube into the sink. Give one mark for identifying the gas as chlorine and giving an appropriate test, e.g. bleaches indicator paper 6 Give one mark for correctly identifying the cation as Pb2+ and giving one pieces of supporting evidence Give one further mark for a second piece of supporting evidence Give one mark for correctly identifying FA 4 as an oxidising agent/oxidant Give one mark for giving a correct piece of evidence to support this behaviour. 4 Total for Question 2 = 10 Total for Paper = 25