PJC_H2 Chemistry_2008 JC2 H2 Chemistry Prelims Paper 3

PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2008 CHEMISTRY 9746/03 Higher 2 Paper 3 Free Response 11 September 2008 2 hours Additional Materials: Data Booklet Writing Paper Cover Page READ THESE INSTRUCTIONS FIRST Write your name, CT Group and index number in the spaces at the top of this page and every sheet of your scripts. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Answer any four questions. Write your answers on the writing papers provided. Begin each question on a fresh page. If there is no answer to any of the questions, a blank sheet of paper for each unanswered question with the question number(s) must still be submitted. 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 with the Cover Page on top. Indicate clearly on the Cover Page the questions you have attempted. This document consists of 7 printed pages. [Turn Over

2 Answer any four questions. 1 (a) When a sample containing 2 moles of SO 2Cl2 is placed in a 2.0 dm 3 vessel at 30°C, it decomposes to SO2 and Cl2 as shown in the equation below. SO2Cl2(g) ⇌ SO2(g) + Cl2(g) ΔH negative At equilibrium, the total pressure of the mixture is determined to be 38.9 atm. (i) Assuming the gases behave ideally, ca lculate the number of moles of each gas present at equilibrium. [4] (ii) Hence, calculate the value of Kc, giving its units. [2] (iii) State Le Chatelier’s principle. [1] (iv) State and explain ho w the value of K c would change if there was an increase in temperature. [2] (b) The chlorides of sodium and silicon di ffer considerably in their physical and chemical properties. State and account for one difference in the (i) physical property (ii) chemical property of the two compounds, writing equations where appropriate. [6] (c) Propose a reaction scheme (in not more than 3 steps) for each of the following conversions. Give the reagent s and conditions, as well as the structures of the intermediate compounds formed. [5] (i) CH3CH2CH2NH2 from CH3CH2OH (ii) CH3COCH2OH from CH3CH=CH2 [Total: 20] 2 (a) (i)