SRJC_H2_CHEM_P3

SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CHEMISTRY 9746/03 Preliminary Examination Paper 3 Free Response 20 August 2009 2 hours Candidates answer on separate paper. Additional Materials: Answer Paper 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 work. 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 the brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. This document consists of 9 printed pages and 1 blank page SRJC 2009 9746/03/Prelim/2009 [Turn over

2 SRJC 2009 9746/03/Prelim/2009 [Turn over Answer any four questions. 1 (a) A student dissolved 8.4 g of sodium fluoride in 250 g of water. Given the following data, calculate the initial temperature of water if the final temperature of the solution is 20.0 °C. Assume that the specific heat capacity of sodium fluoride solution is 4.2 J g–1 K–1. Lattice energy of NaF –918 kJ mol–1 Enthalpy change of hydration of F- –457 kJ mol–1 Enthalpy change of hydration of Na+ –390 kJ mol–1 [3] (b) In the manufacture of fuel for industries, liquid MTBE is added as a solvent to petroleum to reduce pollution. C CH3 CH3 CH3 O CH3 Methyl t-butyl ether (MTBE) (i) What is meant by the term standard enthalpy change of formation of MTBE ? Support your answer with the aid of an appropriate equation with state symbols. (ii) Use the following data and by means of an appropriate energy cycle, prove that the bond energy for the C–H bond in MTBE is +418 kJ mol-1. Enthalpy change of atomisation of C(s) +715 kJ mol–1 Enthalpy change of formation of MTBE –383 kJ mol–1 Enthalpy change of vapourisation of MTBE +30.4 kJ mol–1 Bond Energy of H-H +436 kJ mol–1 Bond Energy of O=O +496 kJ mol–1 Bond Energy of C-O +360 kJ mol–1 Bond Energy of C-C +350 kJ mol–1 (iii) Suggest a reason for the difference in the C–H bond energy in (b)(ii) from the value given in the Data Booklet. [7]

3 SRJC 2009 9746/03/Prelim/2009 [Turn over (c) Magnesium chloride, MgC l2, is an important coagulant used in the preparation of soy products. The lattice energy of magnesium chloride is given to be –2490 kJ mol–1. (i) How would you expect the numerical magni tude of the lattice energy of barium chloride, BaCl2 (s) to compare with that of MgC l2 (s)? Hence predict a likely value for the lattice energy of barium chloride. (ii) The enthalpy cha