MSHS 2024 Chem Prelim Paper 2

Class/ Index Number / Centre Number/ ‘O’ Level Index Number / Name MARIS STELLA HIGH SCHOOL PRELIMINARY EXAMINATION SECONDARY FOUR CHEMISTRY 6092/02 Paper 2 15 August 2024 1 hour 45 minutes Candidates answer on the Question Paper. No additional materials are required. READ THESE INSTRUCTIONS FIRST Write your class, index number, Centre number, O level index number and name 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. 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 24. The use of an approved scientific calculator is expected, where appropriate. For Examiner’s Use Section A Section B Total This document consists of 24 printed pages. 70 10 80

2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 70. 1 The position of seven elements from Period 1 to 4 of the Periodic Table is represented by letters A, B, C, D, E, F and G as shown below. The letters do not represent the chemical symbols of the elements. A D F G B C E Use the letters, A to G, to answer the following questions. They can be used once, more than once, or not at all. (a) Which element contains the smallest number of protons in each atom? …………………………………………………………………………………………….............[1] (b) Which element combines with element F to form a compound which has a low boiling point? …………………………………………………………………………………………….............[1] (c) Which element is the strongest reducing agent? …………………………………………………………………………………………….............[1] (d) Which element has common oxidation states of +2, +4, +6 and +7? …………………………………………………………………………………………….............[1] (e) Which element is important in providing an inert atmosphere for reactions? …………………………………………………………………………………………….............[1] [Total: 5]

3 2 A student investigated the change in mass when hydrated cobalt chloride was heated. The word equation for the reaction is shown below: hydrated cobalt chloride → anhydrous cobalt chloride + water 2.0 g of hydrated cobalt chloride was heated in a test-tube gently for 30 seconds. The test-tube and its contents was cooled and the mass of the test-tube and contents was measured. The experiment was repeated until the mass of the test-tube and contents does not change. (a) Explain why the mass of the test-tube and contents decreased. ……………………………………………………………………………………………………..[1] (b) Suggest why the test-tube and contents were heated until the mass did not change. ……………………………………………………………………………………………………..[1] (c) Energy is taken in from the surroundings when hydrated cobalt chloride is heated. When 238 g of hydrated cobalt chloride is heated until the mass does not change, 88.1 kJ of energy is taken in. The student heated 2.00 g of hydrated cobalt chloride until the mass did not change. Calculate the energy taken in during this reaction. [2] (d) What type of reaction takes place when hydrated cobalt chloride is heated? ……………………………………………………………………………………………………..[1] [Total: 5]

4 3 A student sets up an experiment as shown in Fig 3.1 to study the effect of graphite and copper electrodes in the electrolysis of aqueous copper(II) sulfate. Fig 3.1 (a) With the aid of half equations, describe one difference in the observation at the anodes in both beakers. ……………………………………………………………………………………………................. ……………………………………………………………………………………………................. ……………………………………………………………………………………………................. ……………………………………………………………………………………………................. …………………………………………………………………………………………….............[2] (b) The mass of the substance (m) deposited or liberated at any electrode is directly proportional to the quantity of electricity or charge (Q) passed. In the experiment, 289500 coulomb of charge (Q) passed through the circuit. These charges are carried by electrons. Given that the Faraday’s constant is 96 500 coulomb per mole and using the following equation: Q = number of moles of electrons x Faraday’s constant copper electrodes graphite electrodes aqueous copper(II) sulfate aqueous copper(II) sulfate

5 (i) Calculate the number of moles of electrons supplied. [1] (ii) Calculate the mass of copper formed in beaker B. [2] (c) The student repeated the experiment. She replaced copper(II) sulfate solution in beaker B with sodium sulfate solution and added a few drops of Universal Indicator at the start of the experiment. Describe the change you would observe to the colour of solution in beaker B near the cathode during the experiment. Explain your answer. ……………………………………………………………………………………………................. ……………………………………………………………………………………………................. …………………………………………………………………………………………….............[2] [Total: 7]

6 4 Titanium is a transition metal. It is extracted from titanium dioxide in a two-stage industrial process as shown below. Stage 1: TiO2 + 2 C + 2 Cl2 TiCl4 + 2 CO Stage 2: TiCl4 + 4 Na Ti + 4 NaCl (a) Suggest one hazard associated with Stage 1. ……………………………………………………………………………………………………..[1] (b) Suggest why the reaction in Stage 2 is carried out in an atmosphere of argon and not in air. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………..[2] (c) Titanium chloride is a liquid at room temperature. Explain why you would not expect titanium chloride to be a liquid at room temperature. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………..[2] (d) In Stage 2, 40 kg of titanium chloride was added to 20 kg of sodium. (i) Determine the limiting reactant. Show your calculations clearly. [3] (ii) For a Stage 2 reaction , the percentage yield was 92.3% . The theoretical maximum mass of titanium produced was 13.5 kg. Calculate the actual mass of titanium produced. [1] [Total: 9]

7 5 This question is about iron and its compounds. (a) The ease of reduction of four metal oxides by heating with carbon is shown in Table 5.1. Table 5.1 metal oxide ease of reduction with carbon chromium(III) oxide only reduced above 1700 °C iron(III) oxide reduced above 650 °C magnesium oxide not reduced at 1750 °C nickel(II) oxide only reduced above 300 °C Using information from Table 5.1, state and explain the reactivity of the metals in decreasing order. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………..[3] (b) Potassium is a metal in Group 1 of the Periodic Table. Describe two properties of iron which differ from those of potassium. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………..[2] (c) When iron reacts with dilute hydrochloric acid, iron(II) chloride solution is formed. (i) Describe a test for iron(II) ions and the expected results. …………………………………………………………………………………………………. ………………………………………………………………………………………………[2] (ii) Another chloride of iron has the structure shown below. . Deduce the molecular formula o