BTYSS 2024 FYE 4E CHEM P2

BEATTY SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS CANDIDATE NAME CLASS REGISTER NUMBER CHEMISTRY 6092/02 Paper 2 16 August 2024 Setter: Mdm Stella Soh 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. Write your answers in the spaces provided. Section B Answer one question. Write your answers 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 22. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use A 70 B…. 10 Total 80 This document consists of 22 printed pages and 0 blank page. [Turn over

2 Section A Answer all questions in this section in the spaces provided. A1 The formulae of some elements and compounds are listed. I2 ZnCl2 BaCl2 PbO KI CuCO3 PbBr2 SO2 Answer the following questions using elements or compounds from the list. You may use each element or compound once, more than once or not at all. (a) Which substance can react with both an acid and an alkali? ………………………………………………………………………………………… [1] (b) Which substance in aqueous form reacts with aqueous chlorine to form a brown solution with black crystals? ………………………………………………………………………………………… [1] (c) Which substance has a mass of 8.00 g for every 0.125 mol? ………………………………………………………………………………………… [1] (d) Which substance can be prepared by precipitation? ………………………………………………………………………………………… [1] (e) Which substance produces a red dish brown vapour when electricity is passed through its molten state? ………………………………………………………………………………………… [1] [Total: 5]

3 A2 Chlorine exists as two isotopes, chlorine-35 and chlorine-37. (a) In a sample of 100 chlorine atoms, there are 76 atoms of chlorine-35 and 24 atoms of chlorine-37. Find the average relative atomic mass of this chlorine sample. average relative atomic mass = ………………………… [1] (b) An element T is found in period 3 of the Periodic Table. It reacts with chlorine to form a chloride with a formula T2Cl2, which has a melting point of −80C and a boiling point of 137C. (i) Use ideas about bonding and structure to explain why T2Cl2 is a liquid at room temperature and pressure. ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (ii) Draw a ‘dot and cross’ diagram to show the arrangement of the outer shell electrons in T2Cl2. [2] [Total: 5]

4 A3 Sodium chlorate(V), NaClO3, is used in some aircrafts as a source of emergency oxygen when there is a drop in cabin pressure. The catalyst, iron powder , is mixed with sodium chlorate(V) and can be ignited by a charge, which is activated by pulling on the emergency mask. Some information on sodium chlorate(V) is shown. NaClO3 melting point/C 248 boiling point/C -- (a) Sodium chlorate(V) decomposes as shown. 2NaClO3 (s) → 2NaCl (s) + 3O2 (g) (i) What does (V) in sodium chlorate(V) indicate? …………………………………………………………………………………. [1] (ii) The decomposition of sodium chlorate(V) is a redox reaction. Use oxidation states to show that this statement is true. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (iii) After the catalytic decomposition of sodium chlorate( V), the catalyst, iron is mixed with the sodium chloride product. Describe how sodium chloride salt can be separated, if all the sodium chlorate(V) has fully decomposed. ………………………………………………………………………………………… …………………………………………………………………………………. [1] (b) Suggest why there is no data for the boiling point in the table for sodium chlorate(V). ………………………………………………………………………………………… [1] (c) If 5.00g of impure sodium(V) chlorate can decompose to form 450 cm3 of oxygen gas, calculate the percentage purity of sodium(V) chlorate in the sample. [3] [Total: 8]

5 A4 Methane, methanol and hydrogen have been investigated as possible alternative fuels for motor vehicles that currently use petrol. The table below compares the energy released on combustion of these fuels. The enthalpy change of combustion of a substance, H, is defined as the energy released when one mole of the substance is completely burnt in oxygen. Table 4.1 fuel density/g/dm3 H/ kJ/mol petrol 710 - 770 − methane 0.667 −891 methanol 792 −726 hydrogen 0.0884 −286 (a) Suggest a reason why no value is quoted for the enthalpy change of combustion of petrol in Table 4.1. ………………………………………………………………………………………………. ………………………………………………………………………………………… [1] (b) Methane and methanol undergo complete combustion to give the same products. (i) Write a chemical equation for the combustion of methane. …………………………………………………………………………………. [1] (ii) Explain why the enthalpy change of combustion of methane is more negative than the enthalpy change of combustion of methanol. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………. [2] (iii) Draw the energy profile diagram for the reaction in (b)(i). Label on the diagram the activation energy and the enthalpy change. [3] energy progress of reaction

6 (c) Although the combustion of hydrogen releases less energy as compared to methane per mole, many people believed that hydrogen is a better alternative fuel compared to methane, in terms of environment impact. Suggest why is this so. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………… [2] (d) One alternative fuel technology involves the conversion of liquid methanol into hydrogen gas as shown by the chemical equations below. The hydrogen obtained can then be used as a fuel. Step 1: CH3OH (l) → CH3OH (g) Step 2: CH3OH (g) → 2H2 (g) + CO (g) Suggest why this alternative fuel technology to produce hydrogen is sometimes said to have a harmful effect. ……………………..…………………………….………………………………………….. …….……………....…………………………….………………………………………….. …………...…………………………………………………………………………… [1] [Total: 10]

7 A5 To in vestigate the rate of reaction between magnesium and an excess of dilute hydrochloric acid, Amy set up an experiment as shown in Fig. 5.1. Fig. 5.1 (a) Explain why Amy added dilute hydrochloric acid in excess. ………………………………………………………………………………………………. ………………………………………………………………………………………... [1] (b) Explain, in terms of collisions and energy, how the rate of reaction would be affected if the concentration and the temperature of the acid is increased in Fig 5.1. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………… [3] (c) During the experiment, the small piece of magnesium kept rising to the surface. Suggest a reason why the small piece of magnesium kept floating to the surf