ACJC_Chemistry_Paper 3_Questions Prelims

Centre Number Index Number Name and Class ANGLO-CHINESE JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Advanced Level CHEMISTRY 9746/03 Higher 2 Paper 3 Free response 18 August 2008 2 hours Candidates answer on separate paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, Centre number and index number on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagram, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together including the cover page. Write down the question numbers that you have attempted in the table below. For Examiner's Use Question no. Marks TOTAL This question paper consists of 8 printed pages including the cover page.

Paper 3 (80 marks) Answer any four questions 1 (a) When aqueous bromine reacts with methanoic acid, carbon dioxide gas is produced. Br 2 (aq) + HCOOH (aq) 2 Br - (aq) + 2 H+ (aq) + CO2 (g) The rate of the reaction can be determined by measuring the rate of formation of carbon dioxide gas. In investigations of this reaction, the following results were obtained. Initial concentrations / mol dm -3 Experiment [Br2] [HCOOH] Initial rate of formation of CO2 (g) / mol dm-3 s-1 1 0.01 0.02 2.0 x 10-6 2 0.02 0.04 8.0 x 10-6 3 0.03 0.02 6.0 x 10-6 (i) Deduce the order of the reaction with respect to Br2 and HCOOH. Hence, write a rate equation for the reaction. [3] (ii) Using the data from Experiment 3 , calculate the rate constant for the reaction, stating its units. [2] (iii) What conclusions about the mechanism of the reaction can you draw from the rate equation? [2] (iv) In another experiment, equal volumes of 0.01 mol dm -3 of Br 2 and 0.02 mol dm -3 of HCOOH were mixed. What is the initial rate of this experiment? [2] (b) The relative molecular mass and the boiling point of methanal, methanol and methanoic acid are given in the table below. Compounds Relative Mo