JPJC Prelim 2025 Paper 2 QP_H2 Chem

© Jurong Pioneer Junior College [Turn Over NAME CLASS 24S JURONG PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION 2025 CHEMISTRY 9729/02 Paper 2 Structured Questions 29 August 2025 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and index number in the spaces at the top of this page. Write in dark blue or black pen. You may use a 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. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 16 2 11 3 14 4 18 5 16 Penalty (delete accordingly) Lack 3sf in final answer –1 / NA Missing/wrong units in final ans –1 / NA Bond linkages –1 / NA Total 75 This document consists of 20 printed pages.

2 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2025 Answer ALL the questions in the spaces provided. 1 Nitrogen is found in inorganic compounds such as the oxides of nitrogen, NO 2 and NO. For Examiner’s Use (a) NO2 can be produced from the thermal decomposition of gaseous N2O5. 2N2O5(g) → 4NO2(g) + O2(g) H1 Table 1.1 gives some data relevant to this question. Table 1.1 process H / kJ mol−1 standard enthalpy change of formation of N2O5(g) +11.3 standard enthalpy change of formation of NO(g) +89.0 NO(g) + 1 2 O2(g) → NO2(g) −58.1 (i) Explain what is meant by standard enthalpy change of formation. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [1] (ii) Use data from Table 1.1 to calculate H1. You may find it helpful to draw an energy cycle. [2]

3 © Jurong Pioneer Junior College 9729/02/J2 PRELIMINARY EXAM/2025 [Turn Over (iii) In the solid state, N 2O5 has an ionic structure and consists of the ions, NO2+ and NO3−. Draw and name the shapes of NO2+ and NO3−. For Examiner’s Use ion NO2+ NO3− diagram of shape name of shape [3] (b) Nitrogen dioxide, NO 2, and dinitrogen tetraoxide, N 2O4, exist in dynamic equilibrium with each other. N2O4(g) = 2NO2(g) H = +58 kJ mol−1 At 50 C and a pressure of 1.68  105 Pa, 4.60 g of the equilibrium gaseous mixture occupies 1.00 dm3. (i) Assuming the gaseous mixture behaves ideally, calculate the average relative molecular mass, Mr, of the gaseous mixture. [1] (ii) Using the following relationships, calculate the mole fraction of N 2O4, m, and the mole f