MI_H1_CHEM_8873_02

Class Adm No Candidate Name: This question paper consists of 17 printed pages and 1 blank page. 2018 End-of-Year Exams Pre-University 2 H1 CHEMISTRY 8873 / 02 Paper 2 Structured Questions 11 Sept 2018 2 hours Candidates answer on the Question paper. Additional materials: Data Booklet READ THESE INSTRUCTIONS FIRST Do not turn over this question paper until you are told to do so Write your name, class and admission number 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 all questions. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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. Question 1 2 3 4 5 Section B Total Marks 15 10 15 9 11 20 80

2 Section A Answer all questions in the spaces provided. For Examiners’ Use 1 In acidic solution, bromate(V) ions, BrO3–, oxidises bromide ions to bromine. The progress of the reaction may be followed by adding a fixed amount of phenol (an aromatic alcohol) together with methyl red indicator. The bromine produced during the reaction reacts very rapidly with phenol. When all the phenol is consumed, any excess bromine bleaches the indicator immediately. The initial rate of formation of Br 2 is indicated by the time taken for the bromine to bleach the indicator. (a) An experiment was carried out four times at room temperature. The total volume of the reaction mixture is the same in all four experiments and the following data were obtained. Experiment [BrO3–] / mol dm–3 [Br –] / mol dm–3 Initial rate of formation of Br2 / mol dm–3 s–1 1 0.10 0.10 8 x 10 –2 2 0.10 0.05 4 x 10 –2 3 0.05 0.05 2 x 10 –2 4 0.05 0.10 4 x 10 –2 (i) Determine the order of the reaction with respect to each of the following reactants, showing your working clearly. I. BrO3– II. Br – [3] (ii) Based on your answer in (a)(i), sketch a concentration-time graph for BrO3 -. [1]

3 [Turn over (iii) Describe, and explain in molecular terms, how the rate of reaction is affected by an increase in temperature. You should make reference to the Boltzmann distribution in your answer. For Examiners’ Use ……………………………………………………………………………………………………... ........... ……………………………………………………………………………………………………... ...........