2022 JPJC Prelim Paper 4 QP with Mark Schemes

© Jurong Pioneer Junior College [Turn Over NAME Mark Schemes CLASS 21S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2022 CHEMISTRY 9729/04 Higher 2 Paper 4 Practical 16 August 2022 2 hours 30 minutes Candidates answer on the Question paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your name, class and exam index number 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 a HB pencil for any diagrams, 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 18 and 19. Shift At the end of the examination, fasten all your work securely together. Laboratory The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 3 4 Total This document consists of 19 printed pages.

2 © Jurong Pioneer Junior College 9729/04/J2 PRELIMINARY EXAM/2022 Answer all the questions in the spaces provided. 1 Determination of the percentage by mass of iron in a sample of iron wire Iron wire contains impurities. You will investigate the percentage by mass of iron in a sample of iron wire. A sample of iron wire is reacted with an excess of sulfuric acid to produce a solution of iron(II) sulfate. Fe(s) + H2SO4(aq) → FeSO4(aq) + H2(g) You will titrate the solution of iron( II) sulfate with potassium manganate(V II) of known concentration to determine the amount of iron(II) ions present and hence the percentage by mass of iron in the wire. You may assume the impurities do not form any products that react with potassium manganate(VII). 5Fe2+(aq) + MnO4–(aq) + 8H+(aq) → 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) FA 1 is a solution of FeSO 4 prepared by reacting 3.03 g of iron wire with sulfuric acid to make 500 cm3 of solution. FA 2 is 3.16 g dm–3 potassium manganate(VII), KMnO4. FA 3 is 1.00 mol dm–3 sulfuric acid, H2SO4. (a) Method 1. Fill the burette labelled “FA 2” with FA 2. 2. Pipette 25.0 cm3 of FA 1 into a conical flask. 3. Use the 50 cm3 measuring cylinder to transfer 25 cm3 of FA 3 to the same conical flask. 4. Titrate this mixture with FA 2 until a permanent pale pink colour is obtained. 5. Record your titration results, to an appropriate level of precision, in the space provided below. 6. Repeat points 2 to 5 until consistent results are obtained. Results Final burette reading / cm3 25.30 25.30 Initial burette reading / cm3 0.00 10.00 Volume of FA