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kimia Chapter 6

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  • 1. CURICULUM DEVELOPMENT CENTRE POST TEST TOPIC: ELECTROCHEMISTRY Time: 15 minutes Answer all questions. Write your answers in the spaces provided in the table below. Post Test Answer Table Question 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. No. Answer 1 Figure 1 shows the set-up of apparatus for electrolysis. Carbon electrodes Electrolyte Figure 1 Which of the following compounds could be used as an electrolyte? A Ethanol B Glucose solution C Molten acetamide D Sodium hydroxide solution 2 Which of the following conducts electricity entirely by the movement of its ions? A Molten Sodium B Molten lead(II) bromide C Molten naphthalene D Mercury
  • 2. 3 The apparatus shown in Figure 2 was set-up. Electrodes Substance X Figure 2 Which of the following substance X causes the bulb to light up when electricity passes through it? A Ethanol B Molten naphthalene C Solid potassium chloride D Aqueous hydrochloric acid 4 Molten magnesium oxide is electrolysed using carbon electrodes. Which equation represents the half reaction at the cathode? A Mg2+ + 2e → Mg B 2H+ + 2e → H2 C 4OH- → 2H2O + O2 + 4e D 2O2- → O2 + 4e 5 Figure 3 shows an electrolytic cell. Electrodes Methylbenzene Figure 3 Which of the following statements explain why the light bulb does not light up? A Methylbenzene is not soluble in water B Methylbenzene has strong covalent bonds. C Methylbenzene has no free mobile ions. D Methylbenzene has low melting point 6 What are the ions present in molten sodium bromide? A Na+ and Br- B Na2+ and Br2- C Na+ and Br2- D Na2+ and Br- 63
  • 3. 7 In the electrolysis of molten sodium chloride using carbon electrodes, which of the following half-equation represents the reaction at the anode? A 4OH-(aq) → 2H2O(l) + O2(g) + 4e B Na+(l) + 2e → Na(s) C 2Cl-(l) → Cl2(g) + 2e D 2H+(aq) + 2e → H2(g) 8 What happens when molten lead(II) bromide is electrolysed using carbon electrodes? A Lead(II) ions receive electrons at the anode B Lead(II) ions lose electrons at the cathode C Bromide ions receive electrons at the cathode D Bromide ions move towards the anode 9 Which of the following equation would represent the reaction that occurs at the cathode during electrolysis of molten lead(II) bromide? A 2Br- → Br2 + 2e B 2Br- + 2e → Br2 C Pb2+ → Pb + 2e D Pb2+ + 2e → Pb 1 An electrolysis process is carried out using apparatus as shown in Figure 4. 0 Carbon Carbon Liquid Y Liquid X Figure 4 One of the beaker contains liquid X and the other beaker contains liquid Y. Which of the following pairs of liquid will light up the bulb? Liquid X Liquid Y A Mercury Hexene B Sodium chloride solution Ethanol C Molten lead(II) bromide Dilute sulphuric acid D Copper(II) nitrate Molten acetamide 1 Lead(II) iodide does not conduct electricity because 1 A It is a solid B It is a covalent compound C It is insoluble in water D The lead(II) ions and bromide ions are not free to move 64
  • 4. 1 Which of the following occur during the electrolysis of molten sodium bromide? 2 I Bromide ion accept electron from the anode II Electrons move from cathode to anode III Sodium ions are attracted to cathode IV Bromide ions move towards anode A II and IV only B I and III only C III and IV only D I, II and III only 1 What are the products of the electrolysis of molten lead(II) iodide using carbon 3 electrodes? Anode Cathode A Hydrogen Oxygen B Oxygen Hydrogen C Iodine Lead D Lead Iodine 1 Figure 5 shows the electrolysis of molten potassium iodide in the laboratory. Which of 4 the following observations would be obtained? Carbon electrodes Molten potassium iodide Figure 5 Anode Cathode A Brown gas released Shining grey metal formed B Purple vapour released Shining grey metal formed C Greenish yellow gas released Shining grey metal formed D Shining grey metal formed Colourless gas formed 1 Which of the following statements are true about an electrolyte? 5 I Electrolyte can conduct electricity in solid state II Electrolyte can conduct electricity in the molten state or in aqueous solution III Electrolyte contains freely moving ions IV Electrolyte can be decomposed by electric current A I and III only B II, III and IV only 65
  • 5. C I, II and III only D I, II, III and IV 66