JJC_H2_CHEM_P2

JURONG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS CHEMISTRY 9746/02 Paper 2 Structured 25 August 2009 1 hour 30 minutes Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. 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. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. A Data Booklet is provided. Do not write anything on the Data Booklet. 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 5 6 7 Total This document consists of 15 printed pages and 2 blank pages. [Turn over Page 1 of 15

1. (a) The volume of a sample of SO 2 was monitored at various pressures while keeping temperature constant. The following results were obtained. P/ kPa V/ m 3 PV/ kPa m3 6.0 0.375 12.0 0.188 18.0 0.125 (i) Draw diagrams to illustrate the shape of SO2 and SO3 molecule. Include the name of the shape in your diagrams. (ii) For each pressure stated above, calculate the values of PV, giving each of your numerical answers to one decimal place. (iii) Using your answer (a)(ii), deduce with justification whether the sample of SO 2 is behaving ideally. ………………………………………………………………………………….. (iv) Suggest a reason for this behaviour of SO2 in the sample. [7] Page 2 of 15

1. (b) A 2:1 mixture by volume of SO 2 and O 2 at an initial pressure of 15 atm is allowed to reach equilibrium at 250 °C. 2SO2 (g) + O2 (g)  2SO3 (g) The equilibrium pressure was found to be 11 atm. (i) Calculate the partial pressure of each gas at equilibrium. (ii) Hence calculate the value of K p, stating its units. (iii) State and explain the effect of lowering pressure on the yield of SO3. ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… ………………………………………………………………………………… [6] Page 3 of 15

1. (c) (i) 2SO2 (g) + O2 (g)  2SO3 (g) H = 197 kJ mol-1 The enthalpy change of atomisation of oxygen is +248 kJ mol-1. On the grid below, incorporate these enthalpy changes into an energy cycle for calculating the average bond energy of S=O bond. (ii) Hence calculate the average bond energy of the S=O bond. [3] [Total: 16] Energy/ kJ mol -1 Page 4 of 15

2. (a) When dissolved in water, iron( III) chloride undergoes hydrolysis and gives off heat in an exothermic reaction. The resulting brown solution is acidic. Given the charge dens