NYJC_Prelim_CHEM_P2 ANS

NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 Answers CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 9746/02 Paper 2 Structured 23 September 2009 1 hour 30 minutes Candidates answer on the Question 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 working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. 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. For Examiner’s Use 1 9 2 16 3 8 4 10 5 13 6 4 Total 60 This document consists of 12 printed pages and 0 blank page. [Turn over

2 H2 Chemistry 9746/02/NYJC J2/09 PX [Turn Over For Examiner's Use Answer all questions. 1 (a) The use of the Data Booklet is relevant to thi s question. Nitrogen dioxide disproportionates in ac idic solution to nitrous acid and nitrate ions. (i) Write a balanced equation for the disproportionation reaction. [1] 2NO2 + H2O → HNO2 + NO3 ─ + H+ (ii) Use the data below and any other rele vant data in the Data Booklet to determine if this disproportionation r eaction would actually occur under standard conditions NO2 + H+ + e HNO2 Eθ = +1.10 V [2] NO2 + H+ + e HNO2 Eθ = +1.10 V NO3 ─ + 2H+ + e NO2 + H2O Eθ = +0.81 V 2NO2 + H2O → HNO2 + NO3 ─ + H+ Eθ cell = (+1.10) - (+0.81) = +2.9 V Hence disproportionation is favourable (b) A 0.360 g sample of gaseous aluminium chloride takes up a volume of 52 cm3 at a temperature of 200oC and a pressure of 1.02 x 105 Pa. (i) Under what conditions of temperat ure and pressure would you expect the behaviour of gaseous aluminium chloride to be most like that of an ideal gas? [1] High temperature and low pressure. (ii) Calculate the Mr of the vapour at this temperature. [2] Mr = 56 0.360 8.31 (273 200) 2671.02 10 52 10 RT massPV      (c) Compounds of aluminium have many important uses industrially. For

3 For Examiner's Use example in the H aber process, Al 2O3 are mixed with ir on catalyst to enhance efficiency of the iron catalyst. Ammonia is manufactured in the Haber process according to the equation: N2 (g) + 3H2 (g) 2NH3 (g) ΔH = -92 kJm