VJC 2022 H2 Chem Prelim P3_ans_

1 © VJC 2022 9729/03/PRELIM/22 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 ……………………………………………….………….. …………………………….. CHEMISTRY 9729/03 Paper 3 Free Response Candidates answer on the Question Paper. Additional Materials: Data Booklet 19 September 2022 2 hours READ THESE INSTRUCTIONS FIRST Write your name and CT group on all the work you hand in. Write in dark blue or black pen. You may use a soft 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. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 / 18 2 / 22 3 / 20 Section B 4 OR 5 / 20 Total / 80 This document consists of 25 printed pages.

2 © VJC 2022 9729/03/PRELIM/22 Section A Answer all the questions in this section. 1 (a) (i) Under what conditions of temperature and pressure would you expect the behaviour of a real gas to be most like that of an ideal gas? [1] • High temperature and low pressure (ii) Barium ethanedioate, BaC 2O4, decomposes on heating to produce a mixture of two different gases, A and B, and an oxide only. Neither gas A nor gas B is an ideal gas. They have the following boiling points. gas boiling point / oC A –191.5 B –78.5 The graph below shows the variation of pV RT with pressure, p, for 1 mol each of gas A and gas B at constant temperature. Identify the graph that corresponds to gas A and explain your choice. [2] • Graph I corresponds to gas A. • Gas A has lower boiling point than B, hence, it has weaker intermolecular forces of attraction leading to less deviation from ideality. (iii) Free volume, V, refers to the volume of space between gas molecules. For an ideal gas, the free volume is essentially the same as the volume of the container. This can be calculated using the ideal gas equation, pV = nRT. The pressure of a 72 g gaseous sample containing gas A and gas B in a container of volume 400 cm3 is measured to be 3.36 ⨯ 107 Pa at 527 oC. Using the ideal gas equation, calculate the free volume of this gaseous sample in cm 3. Assume the gaseous sample has an average Mr = 36. [2] n = 72 / 3