NYJC_2023_H2_Chemistry_9729_P2

[Turn Over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 9729/02 Paper 2 Structured Questions 12 September 2023 2 hours 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. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. 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 /11 2 /20 3 /20 4 /24 Total /75 This document consists of 21 printed pages.

2 H2 Chemistry 9729/02 NYJC J2/2023 PRELIM Answer all the questions in the spaces provided. 1 Nitrosyl chloride, NOCl decomposes at temperatures above 100 oC to form nitrogen monoxide and chlorine as shown in the equation below. 2NOCl(g)  2NO(g) + Cl2(g) (a) (i) A sample of NOCl was allowed to decompose at 150 ºC and 125 atm. Assuming that NOCl behaves ideally, show that its initial concentration is 3.60 mol dm−3. [1] (ii) A student pointed out that the assumption in (a)(i) that NOCl behaves ideally is not valid. Suggest and explain two possible reasons why this may be so. [2]

3 H2 Chemistry 9729/02 NYJC J2/2023 PRELIM [Turn Over (b) (i) In order to determine the rate equation for this reaction, an investigation was carried out at constant temperature for each experiment. The following results were obtained. initial rate / N m−2 s−1 16.2 47.2 78.8 124 172 ρNOCl / N m−2 0.30 0.50 0.66 0.82 0.95 (ρNOCl)2 / N2 m−4 0.09 0.25 0.44 0.67 0.90 Use these data to plot a suitable graph on the grid below to determine the order of reaction with respect to ρNOCl. [3] (ii) Hence, deduce the order of reaction with respect to ρNOCl. [1] (iii) Construct the rate equation for the decomposition of NOC l and state the units of the rate constant. [1]

4 H2 Chemistry 9729/02 NYJC J2/2023 PRELIM (c) Explain, with the aid of a labelled Boltzmann distribution diagram, the effect on a rate constant of increasing temperature from T1 to T2. [2] (d) The reverse of the decomposition reaction can also occur such that NOC l is formed from NO and Cl2. Given that a possible mechanism for