ASRJC 2022 J2 H2Prelim P3 QP

ASRJC JC2 PRELIM 2022 9729/03/H2 [Turn over ANDERSON SERANGOON JUNIOR COLLEGE 2022 JC 2 PRELIMINARY EXAMINATION NAME:______________________________ ( ) CLASS: 22 / _____ CHEMISTRY 9729/03 Paper 3 Free Response Questions 16 September 2022 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class and register number 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. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions Section B Answer one question A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. 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 Paper 3 A1 / 18 Paper 1 (15%) / 30 A2 / 19 Paper 2 (30%) / 75 A3 / 23 Paper 3 (35%) / 80 B4* / 20 Paper 4 (20%) / 55 B5* / 20 Percentage *Circle the question you have attempted Grade This document consists of 32 printed pages.

2 ASRJC JC2 PRELIM 2022 9729/03/H2 Section A Answer all the questions in this section. 1 NO2 has been identified as a pollutant with strong evidence for public health concern. Exposure to NO2 can irritate airways and aggravate respiratory diseases. (a) (i) Draw a dot–and–cross diagram to show the bonding in a molecule of NO2. [1] (ii) The 2s and 2p orbitals of nitrogen atoms can hybridise in the same way as the 2s and 2p orbitals of carbon atoms. State the shape with respect to the nitrogen atom in NO2. Hence, suggest the hybridisation state of nitrogen in NO2. [1] Table 1.1 shows the bond lengths of two nitrogen–oxygen bonds. Table 1.1 Bond N–O N=O Bond length (pm) 136 115 The observed bond length of each nitrogen–oxygen bond in the NO2 is 119 pm. (iii) What do you understand by the term bond length? [1] (iv) With reference to your answers to (a)(i) and (a)(ii), explain the observed bond length in NO2. [2] …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………...

3 ASRJC JC2 PRELIM 2022 9729/03/H2 [Turn over …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………...

4 ASRJC JC2 PRELIM 2022 9729/03/H2 (b) At room temperature, reddish brown n itrogen dioxide , NO 2, dimerises into colourless nitrogen tetroxide, N2O4. The two gases are in dynamic equilibrium as shown. 2 NO2(g) N2O4(g) H = –58.0 kJ mol–1 reddish brown colourless (i) Using your answer in (a)(i), explain why the dimerisation of NO 2 to form N2O4 is an exothermic process. [1] The graph in Fig. 1.1 shows the pressure -temperature (p–T) relationship of two separate gaseous samples in an enclosed volume. At 273 K, the first sample contains 1 mole of helium gas and the second sample contains 1 mole of gaseous N 2O4. As temperature increases, it is observed that the second sample behaves differently from the helium gas in the first sample. Fig. 1.1 (ii) Explain the shape of p–T graph for the second sample in Fig. 1.1. • The steeper slope as temperature increases from 273 K to T K. • The gentler slope as temperature increases after temperature T K. [3] (iii) State the visible observation that would be made for the second sample as the temperature increases. [1] …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... p T / K 0 273 First Sample Second sample T

5 ASRJC JC2 PRELIM 2022 9729/03/H2 [Turn over …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………...