2022 RVHS JC2 H2 CM Prelim P3 (QP)

River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination [Turn over RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 2 1 J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/03 Paper 3 Free Response 20 September 2022 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 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 the questions. Section B Answer one question. Circle the question number of the question you attempted. 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 Question number 1 2 3 4 5 units s.f. Total Marks 17 20 23 20 20 80 This document consists of 28 printed pages.

2 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination Section A Answer all the questions in this section. 1 In the third period of the Periodic Table, there is considerable variation of chemical and physical properties from sodium to argon. (a) The graph below shows the first ionisation energy from sodium to argon. (i) Write an equation to represent the first ionisation energy of sulfur. [1] (ii) Account for the difference in first ionisation energy of Mg and Al. [1] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. (b) Calcium carbonate decomposes when heated to about 700 °C. Copper(II) carbonate also undergoes a similar decomposition reaction when heated. (i) Write a balanced equation for the thermal decomposition of copper carbonate. [1] (ii) By quoting relevant values from the Data Booklet, state and explain if the thermal decomposition temperature of copper( II) carbonate is expected to be lower or higher than that of calcium carbonate. [2]

3 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination [Turn over ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. (c) Write equations, including state symbols, for the reactions of the following compounds with water. In each case, state the pH of the resultant solution. (i) Na2O [1] (ii) SiCl4 [1] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

4 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination (d) When sodium burns in oxygen, it forms a mixture of sodium oxide, Na2O, and sodium peroxide, Na2O2. (i) Explain the difference in the electrical conductivity of sodium and sodium oxide in their solid states. [2] (ii) The peroxide anion in sodium peroxide contains an OO bond. Draw a ‘dot-and-cross’ diagram for sodium peroxide. [1] (iii) When sodium peroxide is added to water, hydrogen peroxide is produced. Explain, in terms of structure and bonding, why hydrogen peroxide is a liquid while sodium peroxide is a solid at room temperature. [2] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

5 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination [Turn over (e) Some Pb metal and a solution of Cr3+(aq) were mixed and allowed to reach equilibrium. Pb(s) + 2Cr3+(aq) = Pb2+(aq) + 2Cr2+(aq) The equilibrium concentrations of Cr3+(aq) and Cr2+(aq) were as follows. [Cr3+(aq)] = 0.200 mol dm–3 [Cr2+(aq)] = 2.96  10–4 mol dm–3 (i) Write the Kc expression for this reaction. [1] (ii) Calculate Kc for this reaction. [2] (iii) State and explain how the addition of water will affect the position of equilibrium for this reaction. [2] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [Total: 17]

6 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination 2 This question is about the chemistry of aluminium and iron. (a) Anodising is a process used to increase the thickness of the oxide layer on the surface of metal parts. Aluminium is a reactive metal that is readily oxidised by oxygen. This forms a layer of aluminium oxide, Al2O3, making it resistant to corrosion. (i) Draw a labelled diagram of the electrolysis cell used to anodise an iPhone, which is made of aluminium. You should include H2SO4(aq) as the electrolyte. [2] (ii) Write chemical equations, with state symbols, to show the reactions occurring at the anode during anodising. [2] (iii) The iPhone has a surface area of 96.2 cm2 to be anodised. Calculate the time needed to form a 0. 3 mm protective layer of A l2O3 on the iPhone if a current of 2.0 A is passed through the set-up. (Density of Al2O3 = 3.95 g cm−3) [3] ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. …………………………………………………………………………………….

7 River Valley High School 9729/03/PRELIMS/22 2022 Preliminary Examination [Turn over ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. (b) Many chemical reactions such as the reaction between peroxodisulfate and iodide ions occur very slowly at room temperature. S2O82− + 2I− → 2SO42− + I2 To spe