2019 TJC H2 Chem Prelim P4 ANS

1 9729/04/TJC Prelims/2019 [Turn over CANDIDATE NAME CIVICS GROUP / CENTRE NO. / INDEX NO. / CHEMISTRY 9729/04 Paper 4 Practical 2 September 2019 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 17 and 18. 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 18 printed pages and 2 blank pages. For Examiner’s Use 1 / 18 2 /12 3 /15 4 / 10 Total / 55 2019 JC2 PRELIMINARY EXAMINATIONS HIGHER 2

2 9729/04/TJC Prelims/2019 [Turn over Answer all the questions in the spaces provided. 1 Determination of the concentration of a solution of hydrogen peroxide Hydrogen peroxide, H 2O2, can be oxidised to give oxygen, O 2. This reaction happens rapidly in the presence of acidified potassium manganate(VII), KMnO4. 2MnO4͞ (aq) + 5H2O2(aq) + 6H+(aq) 2Mn2+(aq) + 5O2(g) + 8H2O(l) To determine the concentration of a solution of hydrogen peroxide, y ou will first dilute the solution and then carry out a titration using acidified potassium manganate(VII), KMnO4. FA 1 is aqueous hydrogen peroxide. FA 2 is 0.0200 mol dm-3 potassium manganate(VII), KMnO4. FA 3 is 1.0 mol dm-3 sulfuric acid, H2SO4. Keep FA 1 for use in Question 4. (a) Method Dilution ● Pipette 25.0 cm3 of FA 1 into the 250 cm3 volumetric flask. ● Add distilled water to make 250 cm3 of solution and shake the flask thoroughly. ● Label this diluted solution of hydrogen peroxide as FA 4. Titration ● Fill the burette with FA 2. ● Pipette 25.0 cm3 of FA 4 into a conical flask. ● Use the measuring cylinder to add 25 cm3 of FA 3 to the conical flask. ● Titrate FA 4 against FA 2 and record your readings in the space below. ● Carry out as many accurate titrations as you think necessary. Results Final burette reading /cm3 20.70 20.80 Initial burette reading /cm3 0.00 0.00 Volume of FA 2 /cm3 20.70 20.80   ● Appropriate headings and units. ● All accurate burette readings recorded to 0.05 cm3. ● Has two uncorrected, a