Copy of AMKSS 2024 Chem P3

1 AMKSS 4E Prelim Exam 6092/03/2024 [Turn Over ANG MO KIO SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS CHEMISTRY 6092/03 Paper 3 16 August 2024 1 hour 50 minutes Setter: Mrs Joselyn Luei Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Name, Class and Index Number in the spaces at the top of this paper. Write in dark blue or black pen. You may use a 2B pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Answer all the questions in the spaces provided on the Question Paper. Notes for qualitative analysis are printed on pages 13 and 14. 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. 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. For Examiner’s use 1 2 3 4 TOTAL This document consists of 14 printed pages. Candidate Name Form Class Index Number

2 AMKSS 4E Prelim Exam 6092/03/2024 1 Mangalloy is made by alloying steel with manganese. The percentage by mass of manganese in mangalloy can be determined by converting all the manganese in the alloy into aqueous manganate(VII) ions and then using the solution to titrate a solution containing iron(II) ions. No indicator is needed for this titration as the products of the reaction are almost colourless and one drop of aqueous manganate(VII) ions in excess produces a permanent pale pink colour. G is an aqueous solution of manganate(VII) ions, MnO 4-. The solution was prepared by converting all the manganese in a 2.12 g sample of mangalloy into manganate(VII) ions and making the final volume up to 250 cm3 by adding water. H is a solution which initially contained 0.0800 mol/dm 3 iron(II) ions dissolved in an unknown acid. (a) Put G into the burette. The colour of G makes it difficult to see the bottom of the meniscus so you should take all your readings using the top of the meniscus. Pipette 25.0 cm3 portion of H into a conical flask. Add G from the burette into the conical flask. At first the purple colour disappears quickly but as more G is added, the colour disappears less quickly. At the end -point, one drop of G produces a pale pink colour that does not disappear on swirling. Record your titration results in the space provided on page 3 , repeating the titration as many times as you consider necessary to achieve consistent results. Show clearly how you obtain an average volume of G to be used in your calculations.

3 AMKSS 4E Prelim Exam 6092/03/2024 [Turn Over Results: