Yuan Ching Prelim P2

1 YUAN CHING SECONDARY SCHOOL Secondary Four Express Course Preliminary Examination 2024 CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 6092/02 Paper 2 23 Aug 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 and name on all the work you hand in. Write in dark blue or black pen. You may use an HB soft pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A (70 marks) Answer all questions. Write your answers in the spaces provided. Section B (10 marks) 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 can be found on Page 26. The use of a scientific calculator is expected, where appropriate. For Examiner’s Use Section A Section B 11: 12: Total / 80 This paper consists of 26 printed pages.

2 Section A [70 marks] Answer all the questions in this section. Write your answers in the spaces provided on the question paper. 1 Choose from the following compounds in Fig. 1.1 to answer the questions. Fig. 1.1 Each compound, A, B, C, D, E and F may be used once, more than once or not at all. State which compound: (a) has a molecule with only 11 atoms [1] (b) is oxidised to form ethanoic acid [1] (c) is an isomer of butene [1] (d) reacts with hydrogen in the presence of a catalyst to make an alkane [1] [Total: 4]

3 2 An experiment in Fig. 2.1 was set up for measuring the rates of diffusion of gases. The time taken for 100 cm3 of some gases at room temperature and pressure to diffuse from this apparatus are shown in the Table 2.1. Table 2.1 gas tested time /s carbon monoxide, CO 132 chlorine, Cl2 211 methane, CH4 100 nitrogen, N2 ? oxygen 141 Fig. 2.1 (a) Name and explain the gas that diffused fastest. [1] (b) Explain in terms of kinetic particle theory why the temperature must be kept constant in this experiment. [2] (c) Suggest the time that 100 cm3 of nitrogen would take to diffuse out of the apparatus. [1] (d) Explain why this apparatus is unsuitable for finding the rate of diffusion for ammonia gas. [1] [Total: 5]

4 3 Table 3.1 shows results of different tests conducted to compare the properties of two dibasic acid, sulfuric acid and tartaric acid, of the same concentration. Table 3.1 acid X Y Universal Indicator red orange volume of gas collected 10 s after reacting with magnesium 14 cm3 6 cm 3 volume of sodium hydroxide required for complete neutralisation of 25.0 cm3 of acid 22.00 cm3 22.00 cm3 (a) Use information from Table 3.1 to explain which is the weak acid. [3] (b) The reaction of acid Y with aqueous sodium hydroxide can be represented by the equation below, where the anion of the acid is given the symbol A. H2A (aq) + 2NaOH (aq) → Na2A (aq) + 2H2O (l) Calculate the concentration of acid Y in mol/dm3, if 0.100 mol/dm3 of sodium hydroxide is used. [3] [Total: 6]

5 4 The halogens are a group in the Periodic Table consisting of six reactive elements. (a) Complete Table 4.1 to show the colour and state of chlorine, bromine and iodine at room temperature and pressure. Table 4.1 halogen colour and state at room temperature and pressure chlorine bromine iodine [2] (b) A jet of chlorine gas is aimed at a filter paper soaked in a solution of sodium bromide. The solution on the filter paper quickly turns brown. (i) Explain why the solution turns brown. [1]

6 (ii) The experiment is repeated twice.  A jet of iodine gas is aimed at a filter paper soaked in a solution of sodium bromide.  A jet of bromine gas is aimed at a filter paper soaked in a solution of sodium iodide. State and explain what you would expect to see in each experiment. [3] (c) Chlorine is an oxidising element. Explain, in terms of electrons, why chlorine is described as an oxidising element. [1] [Total: 7]

7 5 The graph in Fig. 5.1 shows the volume of gas produced with time for some experiments of a metal, M with hydrochloric acid. In all experiments, M forms an ion with a 2+ charge. The mass of M used in each experiment is 0.195 g. Only one of the experiments has an exact stoichiometric ratio of the reactants (i.e. there is no excess of either reactant), while the rest of the experiments have an excess of metal M. Fig. 5.1 (a) Complete Table 5.1 with appropriate answers. Table 5.1 experiment concentration of acid / mol/dm3 volume of acid / cm3 particle size of metals (small or large) a 0.250 20 small b 0.200 30 large c 0.125 20 large d 0.250 [1]

8 (b) Using Collision Theory, account for the differences between graphs a and d. [3] (c) State the experiment (a, b, c or d) that has the exact stoichiometric ratio of reactants. [1] (d) Hence, identify metal M. Show your working clearly. Metal M: …………………………… [3] [Total: 8]

9 6 Car manufacturers are developing fuel cells for use in cars. Fuel cells produce electrical energy from reaction between a fuel and oxygen. Two possible fuels for use in fuel cells are hydrogen and methanol. Table 6.1 gives some data about these two fuels. Table 6.1 (a) The table gives values for the energy change of combustion for each fuel in kJ/mol. (i) Calculate the energy output for 1 g of each fuel. [2] (ii) Use the values you have calculated and information in the table to discuss the advantages and disadvantages of using each fuel in cars. [3]

10 (b) The energy output of a fuel can be shown using an energy profile diagram. In the space below, draw an energy profile diagram for the combustion of methanol. Your diagram should include labels for the reaction enthalpy change and activation energy. [3] [Total: 8]