TJC Prelim P4_Qn_Ans

1 9729/04/TJC Prelims/2017 [Turn over s CANDIDATE NAME CIVICS GROUP / CENTRE NO. / INDEX NO. / CHEMISTRY 9729/04 Paper 4 Practical 28 August 2017 2 hours 30 minutes Candidates answer on the Question Paper. READ THESE INSTRUCTIONS FIRST Write your Civics Group and name on all the work you hand in. Give details of the practical shift 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 fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Qualitative Analysis Notes are printed on pages 14 and 15. 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. Shift Laboratory This document consists of 15 printed pages. For Examiner’s Use 1 / 15 2 / 24 3 / 16 Total / 55 2017 JC2 PRELIMINARY EXAMINATIONS HIGHER 2

2 9729/04/TJC Prelims/2017 [Turn over Answer all the questions in the spaces provided. 1 Determination of change in oxidation number of a transition metal ion, M2+ You are to determine, by titration, the change in oxidation number of a transition metal ion, M2+, when reacted with acidified potassium manganate(VII). FA 1 FA 2 FA 3 is 0.0200 mol dm3 potassium manganate(VII), KMnO4 is 0.0470 mol dm3 transition metal salt, MSO4 is 1.00 mol dm3 sulfuric acid, H2SO4 (a) Method (i) 1. Fill the burette with FA 1. 2. Using a pipette, transfer 25.0 cm3 of FA 2 into the conical flask. 3. Using a measuring cylinder, transfer 25.0 cm3 of FA 3 to the same conical flask. 4. Carry out as many accurate titration s as necessary to obtain consistent results. Add FA 1 until the contents of the conical flask turns a permanent pale pink colour. 5. Record below, in a table form, all of your burette readings and the volume of FA 1 added in each accurate titration. Results Final burette reading /cm3 23.50 23.50 Initial burette reading /cm3 0.00 0.00 Volume of FA 1 /cm3 23.50 23.50   ●Appropriate headings and units for accurate data where headings should match readings. ●All accurate burette readings recorded to 0.05 cm3 ●Has two uncorrected, accurate titres value within ±0.10cm3 ●●●3m – accuracy [6] (ii) From your titrations, obtain a suitable volume of FA 1 to be used in your calculations. Show clearly how you obtained this volume. ●Average titre = 𝟐𝟑.𝟓𝟎+𝟐𝟑.𝟓𝟎 𝟐 = 23.50 cm3 25.0 cm3 of FA 2 required _23.50______________ cm3 of FA 1 [1]