TJC Prelim P4_Ans

1 9729/04/TJC Prelims/2018 [Turn over s CANDIDATE NAME CIVICS GROUP / CENTRE NO. / INDEX NO. / CHEMISTRY 9729/04 Paper 4 Practical 29 August 2018 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 20 and 21. 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 20 printed pages and 1 blank page. For Examiner’s Use 1 / 24 2 / 14 3 / 17 Total / 55 2018 JC2 PRELIMINARY EXAMINATIONS HIGHER 2

2 9729/04/TJC Prelims/2018 [Turn over BLANK PAGE

3 9729/04/TJC Prelims/2018 [Turn over Answer all the questions in the spaces provided. 1 Determination of the concentrations of sulfuric acid and potassium hydroxide FA 1 is a dilute solution of sulfuric acid, H2SO4 FA 2 is a dilute solution of potassium hydroxide, KOH FA 3 is 0.377 mol dm-3 aqueous sodium carbonate, Na2CO3 You are also provided with thymolphthalein solution. Both potassium hydroxide and sodium carbonate are bases which will react with sulfuric acid to give a salt and water – a process known as neutralisation. You will add different volumes of FA 3 to identical samples of dilute sulfuric acid, FA 1. In each case, the volume of sodium carbonate solution you add will only neutralise part of the sulfuric acid. You will then complete the neutralisation of each mixture by titration with dilute potassium hydroxide, FA 2. Analysis of your results using a graph will enable y ou to determine the concentrations of sulfuric acid and that of potassium hydroxide. (a) (i) Preparation and titration of reaction mixtures Prepare four different mixtures of FA 1 and FA 3 as described below. Mixture 1 1. Pipette 25.0 cm 3 of FA 1 into a conical flask. Label the flask 6.00 cm3. 2. Fill a burette with FA 3. 3. Add 6.00 cm 3 of FA 3 into the same conical flask. 4. Thoroughly stir the mixture and set it aside for later use. Mixture 2 Repeat the procedure used for Mixture 1 but this time add 25.0 cm 3 of FA 1 and 20.00 cm3 of FA 3 into a second conical flask. Label the flask 20.00 cm3.