2022 BtySS Chem Prelims P2

BEATTY SECONDARY SCHOOL PRELIMINARY EXAMINATION 2022 SECONDARY FOUR EXPRESS CANDIDATE NAME CLASS REGISTER NUMBER CHEMISTRY 6092/02 Paper 2 19 August 2022 Setter: Mr Yeo Chee Keong 1 hour 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. 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. Section A Answer all questions in the spaces provided. Section B Answer all three questions. The last question is in the form either/or. Answer all questions in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 20. For Examiner’s Use A 50 B7 12 B8 8 B9… 10 Total 80 The use of an approved scientific calculator is expected, where appropriate. This document consists of 20 printed pages and 0 blank page. [Turn over

2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 Use the list of substances to answer the questions. You may use each substance once, more than once or not at all. iodine ozone dichloroethane magnesium potassium manganate(VII) copper(II) sulfate calcium chloride diamond (a) Which substance is a good reducing agent? ………………………………………………………………………………………… [1] (b) Which substance can be formed under ultraviolet radiation conditions? ………………………………………………………………………………………… [1] (c) Which substance exists as three different colours when the physical state is changed? ………………………………………………………………………………………… [1] (d) Which two substances can react to undergo a redox reaction? ………………………………………………………………………………………… [1] (e) Which substances are elements? ………………………………………………………………………………………… [1] [Total: 5]

3 A2 Lithium is a metal with low melting point and low density. It can react with cold water to form lithium hydroxide and hydrogen gas. (a) Write a chemical equation for the reaction of lithium with cold water. ………………………………………………………………………………………… [1] (b) Given that 0.2 g of lithium metal was used in the reaction with an excess of cold water, determine the volume of hydrogen gas produced. [2] (c) Describe how you can determine that the reaction has reached completion. ………………………………………………………………………………………………. ………………………………………………………………………………………… [1] [Total: 4] A3 Hydrochloric acid reacts with methanol to form chloromethane and water in the equation as shown. HCl(aq) + CH3OH(aq) → CH3Cl(g) + H2O(l) (a) Briefly describe a practical method by which the concentration of hydrochloric acid can be determined in a sample. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………… [3]

4 (b) Fig. 3.1 shows how the concentration of hydrochloric acid changes as the reaction proceeds. Fig. 3.1 (i) Deduce the concentration of hydrochloric acid 4 hours from the start of the experiment. concentration = …………………. mol/dm3 [1] (ii) With reference to the graph in Fig. 3.1, explain clearly whether hydrochloric acid or methanol is the limiting reactant. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (iii) Explain why point A in Fig. 3.1 has the fastest rate of reaction. …………………………………………………………………………………. [1]

5 (iv) Enriq thinks that the average rate of the reaction can be determined by the formula as shown: rate at point A + rate at point B + rate at point C + rate at point D 4 Do you agree with Enriq? Explain your answer. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (c) The rate of formation of chloromethane and water can be changed by altering some conditions. (i) Draw on Fig. 3.1, the curve that you would expect if the experiment w as repeated with hydrochloric acid at a higher temperature. [1] (ii) Use ideas about collisions between particles to describe and explain how the rate of a reaction changes when the concentration of hydrochloric acid is increased. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (iii) Use kinetic particle theory to explain why increasing the pressure of the reaction chamber has little or no effect on the rate of reaction. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] [Total: 14]

6 A4 Hydrogen is an important source of fuel as it burns cleanly and has a high energy content per unit mass. Hydrogen can be produced from the steam-methane reforming reaction shown in Step 1. Step 1: CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) H = +206 kJ/mol The carbon monoxide produced can undergo water -gas shift reaction to produce more hydrogen shown in Step 2. Step 2: CO(g) + H2O(g) ⇌ CO2(g) + H2(g) H = −41.0 kJ/mol (a) Based on Step 1 and Step 2 , w rite the overall equation for the production of hydrogen gas. Include the overall enthalpy change. ………………………………………………………………………………………… [2] (b) Give two reasons why it is better to produce hydrogen using both steps of the reaction in (a) than using Step 1 alone. Explain your answer clearly. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………… [4] (c) Another method of hydrogen production is through the electrolysis of pure water as shown. 2H2O(l) → O2(g) + 2H2(g) H = +484 kJ/mol However, this electrolytic process takes place very slowly. Explain why the reaction takes place very slowly and suggest a modification to make the reaction proceed faster. explanation …………………………………………….………………………………….. ………………………………………………………………………………………………. modification ..…………………………….………………………………………………… ………………………………………………………………………………………… [2] [Total: 8]

7 A5 The diagram shows two organic molecules, A and B which can undergo polymerisation. A B (a) State the type(s) of polymerisation that both molecules can undergo. molecule A .…………………………………………….………………………………….. molecule B …………………………………………………………………………... [2] (b) Draw the structure of two repeating units when molecule A undergoes polymerisation. [1] (c) Suggest why polymers made from molecule B show a wider range of properties than polymers made from molecule A. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………… [2] [Total: 5] A6 Ethanol can be manufactured by the hydration of steam with ethene and the fermentation of glucose solution. Table 6.1 shows a comparison of b