Temasek 2024_Prelim_O_Chem_P2_SectB_QP

Name: Index Number: Class: _______ TEMASEK SECONDARY SCHOOL Preliminary Examination 2024 Secondary 4 Express CHEMISTRY 6092/02 Paper 2 (Section B) Total duration for Sections A and B: 1 hour 45 minutes Candidates answer on the Question Paper. No additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. 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 one question from this section. Write your answers in the spaces provided on the question paper. At the end of the examination, submit Section A and B separately. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 7 in Section B. The use of an approved scientific calculator is expected, where appropriate. FOR EXAMINER'S USE Section B /10 This document consists of 7 printed pages and 1 blank page.

2 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School Section B Answer only one question from this section. Write your answers in the spaces provided. B11 Hydrogen peroxide is a colourless liquid. An aqueous solution of hydrogen peroxide reacts with the iodide ions in acidified potassium iodide to form water and iodine. …… H2O2(aq) + ……. H+(aq) + ..….. I ‾(aq) → …… H2O(l) + …… I2(aq) (a) Balance the above ionic equation. [1] (b) Identify the reducing agent in this reaction. Explain your answer using electrons transfer. Reducing agent : …………………………………………………..…… Explanation: …………………………….……………………………………………… …………………………….……………………………………………… [2] (c) Describe the observation seen during the reaction. …………………………….……………………………………………… [1]

3 No part of the paper is to be reproduced without the approval of the Principal of Temasek Secondary School (d) Table 11.1 shows how the speed of this reaction changes when different concentrations of potassium iodide and sulfuric acid are used. The hydrogen peroxide used in the reaction is always in excess and the temperature is kept constant. Table 11.1 experiment concentration of potassium iodide in mol/dm3 concentration of sulfuric acid in mol/dm3 speed of reaction in mol/dm3 per second 1 0.1 0.1 0.00017 2 0.2 0.2 0.00034 3 0.1 0.2 0.00017 4 0.3 0.1 0.00051 5 0.1 0.3 0.00017 Using the information in Table 1 1.1, describe how increasing the concentration of the following reagents affect the speed of reaction. (i) potassium iodide ……………………………………………………………………... ………………………………