2024 Zhenghua Prelim QP

ZHENGHUA SECONDARY SCHOOL PRELIMINARY EXAMINATION 2024 SECONDARY FOUR EXPRESS CHEMISTRY 6092/02 Paper 2 22 Aug 2024 1 hour 45 minutes Students answer on the Question Paper. No Additional Materials are required. Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School Zhenghua Secondary School READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. Write in dark blue or black ink. 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 25. The use of an approved scientific calculator is expected, where appropriate. Name of Setter: Ms Nur Elfianie This document consists of 25 printed pages including the cover page. [Turn over Candidate Name: ______________________________ Index No: _____ Class: _________

2 Section A Answer all questions. 1 Different types of reactions are listed below. combustion precipitation displacement polymerisation electrolysis rusting Use the list to answer the questions. Name the process of, (a) burning petrol in unlimited supply of air ……………...………………………………………………………………………..………….. [1] (b) making barium sulfate from two soluble compounds ……………...………………………………………………………………………..………….. [1] (c) extracting sodium metal from its ore ……………...………………………………………………………………………..………….. [1] (d) oxidising iron metal in the presence of moisture ……………...………………………………………………………………………..………….. [1] [Total: 4]

3 2 Fig. 2.1 shows the apparatus for measuring the rate of diffusion of gases. Fig. 2.1 The time taken for 100 cm3 of argon, methane, nitrogen and oxygen gases at room temperature and pressure, to reach the diffusion plug were recorded. (a) (i) Deduce the order at which the four gases reach the diffusion plug from the first to the last. first ………………………………………..……… ………………………………………..……… ………………………………………..……… last ………………………………………..……… [1] (ii) Explain your answer in (a)(i). ………………………………………………………………..…….……………………….. ……………………………………………………………….………………………………. ………………………………………………………………..…….……………………….. ……………………………………………………………….…………………………... [2] diffusion plug gas water

4 (b) Explain, in terms of kinetic particle theory, why the temperature of the gases has to be kept constant in this experiment. ……………...……………………………………………………………………………..………… ……………...………………………………………………………………………..…………….. ……………...………………………………………………………………………..………….. [2] (c) Suggest the name of another gas that will diffuse faster than the four gases stated. ……………...………………………………………………………………………..………….. [1] (d) Suggest why the apparatus is unsuitable for finding the rate of diffusion of ammonia. ……………...………………………………………………………………………..………….. [1] [Total: 7] 3 Some cars have components made from an alloy of aluminium and silicon. Silicon is extracted from silicon dioxide in sand by heating the sand to 2000 oC in a furnace with carbon. The reaction is shown below. SiO2 + 2C → Si + 2CO Sand also contains small amounts of aluminium oxide. However, aluminium oxide remains in the silicon after the extraction and further processes are needed to remove it. (a) Using ideas about reduction, deduce the relative reactivity of silicon and aluminium. Explain your answer. ……………...……………………………………………………………………………..………… ……………...……………………………………………………………………………..………… ……………...………………………………………………………………………..…………….. ……………...………………………………………………………………………..………….. [2]

5 (b) Table 3.1 shows information about the oxides of carbon, silicon and aluminium. Table 3.1 oxide melting point /○C electrical conductivity carbon monoxide -205 does not conduct in any state silicon dioxide 1600 does not conduct in any state aluminium oxide 2000 conduct in molten Using ideas about bonding and structure, explain the differences in the properties of the three oxides. ……………...………………………………………………………………………..………….….. ……………...……………………………………………………………………………..………… ……………...……………………………………………………………………………..………… ……………...……………………………………………………………………………..………… ……………...……………………………………………………………………………..………… ……………...………………………………………………………………………..……….…….. ……………...………………………………………………………………………..………….. [4] [Total: 6]

6 4 A sample of copper( II) chloride is dissolved in concentrated aqueous potassium chloride and the resulting solution is evaporated. Crystals of the salt produced was found to have the following composition by mass: 31.5% K, 25.6% Cu and the remaining Cl. (a) Calculate the empirical formula of the salt crystal formed. Show all your workings. [3] (b) The ion of an isotope of copper has the formula Cu2+. Complete the table with information about this ion. [2] sub-atomic particles number in Cu2+ electron proton neutron (c) Fluorine gas was bubbled into a separate solution of copper(II) chloride, forming a solution of copper(II) fluoride. With the aid of a chemical equation, explain the chemistry behind this reaction. ……………...……………………………………………………………………………..………… ……………...………………………………………………………………………..……….…….. ……………...………………………………………………………………………..………….. [2] [Total: 7] 66 29 66 29

7 5 Both zinc and iron react with dilute hydrochloric acid. Zn + 2HCl → ZnCl2 + H2 Fe + 2HCl → FeCl2 + H2 (a) (i) 1.65 g sample of zinc is reacted with excess hydrochloric acid. Calculate the volume of hydrogen, measured at room temperature and pressure, formed in this reaction. volume of hydrogen = …………………………………. dm3 [2] (ii) Explain why a different volume of hydrogen, measured at room temperature and pressure, is formed when 1.65 g of iron is reacted with excess hydrochloric acid. ………………………………………………………………..…….……………………….. ……………………………………………………………….……………………..…….. [1] (b) A mixture of iron powder and zinc powder is added to excess sulfuric acid. Describe a chemical test to be carried out on the reacting mixture to show that only zinc has reacted. ……………...……………………………………………………………………………..………… ……………...………………………………………………………………………..……….…….. ……………...………………………………………………………………………..………….. [2] [Total: 5]

8 6 Ozone molecules are continually being broken down and formed in the upper atmosphere of the earth. (a) The equation shows the formation of ozone, O3 in the upper atmosphere. O2 + O → O3 ∆H = - 392 kJ/mol (i) Explain, in terms of bond breaking and bond forming, why this reaction is exothermic. ……………………………………………………………..…….……………………….. ………………………..…………………………………….…………………….…….. [1] (ii) When one mole of oxygen molecules reacts, 392 kJ of energy is released. Calculate the amount of energy released when 48.0 g of oxygen molecules react. energy released = ……………………………. kJ [2] (iii) Compl