GCSE Questions and Answers Redox Chemistry and Electrolysis.

1. Remember that you can search using “edit”! Consider adding your own illustrations. GCSE Questions and Answers Redox Chemistry and Electrolysis. 6 consecutive CCEA GCSE Chemistry papers: 2002-7

2. 2002, Paper 1 3 Electrolysis plays an important part in extracting some metals from their ores and in purifying others.a) Define what is meant by the term electrolysis. _________________________________ ______________________________ [2] b) Name one metal which is obtained from its ore by electrolysis. ______________________________ [1]

3. 3 Electrolysis plays an important part in extracting some metals from their ores and in purifying others.a) Define what is meant by the term electrolysis. Electrolysis is decomposition [1] of a substance using an electric current [1] b) Name one metal which is obtained from its ore by electrolysis. Any reactive metal at the top of the reactivity series. Specification refers to aluminium [1]; but could accept sodium, potassium, calcium, magnesium, zinc.

4. c) Draw a labelled diagram of simple laboratory apparatus which shows how copper can be purified.

5. c) Draw a labelled diagram of simple laboratory apparatus which shows how copper can be purified. Complete circuit (1) (1) (1) (1) (1) Electrolyte (1) Accept any soluble copper salt

6. d) Write balanced, ionic equations to show the electrode reactions which occur when copper is purified.(i) At the anode ________________ [2](ii) At the cathode ______________ [2]

7. d) Write balanced, ionic equations to show the electrode reactions which occur when copper is purified.(i) At the anode Cu → Cu2+ + 2e- [2](ii) At the cathode Cu2+ +2e-→ Cu [2]

8. e) Which particles are responsible for the conductivity of electricity in:(i) metals? ____________________ [1](ii) electrolytes? ________________ [1]

9. e) Which particles are responsible for the conductivity of electricity in:(i) metals? Electrons [1](ii) electrolytes? Ions [1]

10. f) Give two uses of copper metal apart from its use in electrical wiring. _____________________________ ___________________________ [2]

11. Give two uses of copper metal apart from its use in electrical wiring.Specification lists: Plumbing Brass Any two for [1] each Coinage [2]

12. g) The electrolysis of dilute sulphuric acid using inert electrodes produces two gases as products.(i) Name a material which could be used as the electrodes in this experiment. ___________________________ [1](ii) Name the product formed at the anode _______________ cathode _____________ [2]

13. g) The electrolysis of dilute sulphuric acid using inert electrodes produces two gases as products.(i) Name a material which could be used as the electrodes in this experiment. Graphite (or platinum) [1](ii) Name the product formed at the anode oxygen [1] accept O2cathode hydrogen [1] accept H2

14. Write balanced, ionic equations to show how these gases are formed.Anode reaction ______________[2]Cathode reaction _____________[2]

15. Write balanced, ionic equations to show how these gases are formed.Anode reaction2H2O → O2 + 4H+ + 4e-or 4OH- → 2H2O + O2 + 4e-or 4OH- → 4e- + 2H2O + H2 [2]Cathode reaction2H+ + 2e-→ H2 [2]

16. 4 a) What term is used to describe a reaction which gives out heat? __________________________ [1] 2002,Paper 1

17. 4 a) What term is used to describe a reaction which gives out heat?Exothermic [1]

18. b) When drops of water are added to anhydrous copper sulphate heat is given out.(i) Describe what would be observed during this reaction. _________________________________ ______________________________ [2](ii) The addition of water to anhydrous copper sulphate is called ______________________________ [1]

19. b) When drops of water are added to anhydrous copper sulphate heat is given out.(i) Describe what would be observed during this reaction. The white [1] solid would turn blue [1] (ii) The addition of water to anhydrous copper sulphate is called Hydration [1]

20. c) Heat is also given out during the reaction of sodium hydroxide with hydrochloric acid.(i) Give a balanced symbol equation for this reaction. ______________________________ [2](ii) The reaction of an acid with an alkali is called ________________________ [1]

21. c) Heat is also given out during the reaction of sodium hydroxide with hydrochloric acid.(i) Give a balanced symbol equation for this reaction.NaOH + HCl→ NaCl + H2O [2](ii) The reaction of an acid with an alkali is called Neutralisation [1]

22. d) The redox reaction of zinc with copper sulphate solution also gives out heat.(i) Describe what would be observed during this reaction. _________________________________ ______________________________ [2](ii) Give a balanced symbol equation for this equation. _____________________ [2]

23. d) The redox reaction of zinc with copper sulphate solution also gives out heat.(i) Describe what would be observed during this reaction. The silvery/grey[1] zinc would become coated with red/brown[1] copper metal. The blue [1] solution fades / colourless / zinc disappears / bubbles[1] / green[1]. Max [2] (ii) Give a balanced symbol equation for this equation. Zn + CuSO4→ ZnSO4 + Cu or Zn + Cu2+ → Zn2+ + Cu [2]

24. (iii) The reaction of zinc with copper sulphate solution is an example of ______________________________ [1](iv) Explain this redox reaction in terms of electron transfer. _________________________________ _________________________________ _________________________________ ______________________________ [5]

25. (iii) The reaction of zinc with copper sulphate solution is an example of Displacement [1](iv) Explain this redox reaction in terms of electron transfer. The zinc has lost electrons [1] and is therefore oxidised [1]. The copper ions have gained electrons [1] and are therefore reduced [1]. Redox is reduction and oxidation taking place together [1]

26. 1 Aluminium is the most abundant metallic element in the Earth’s crust, making up approximately 8% of the crust. The ore is first purified and the metal is then extracted from the purified ore by electrolysis. 2003, Paper 2

27. a) Explain what you understand by the term “electrolysis”. ______________________________ ___________________________ [2]b) Name the ore from which aluminium is extracted. ___________________________ [1]

28. a) Explain what you understand by the term “electrolysis”.Electrolysis is the breaking down / decomposing / splitting of a substance by passing electricity through it. [2]b) Name the ore from which aluminium is extracted. Bauxite – accept alumina [1]

29. c) The electrolysis of the purified ore is carried out in the Hall-Héroult cell. In this cell the anode and cathode are made of graphite. The electrolyte is molten aluminium oxide dissolved in cryolite, Na3AlF6.

30. (i) Explain what is meant by each of the terms below: Anode _____________________ [1] Cathode ___________________ [1] Electrolyte _________________ [2]

31. (i) Explain what is meant by each of the terms below:Anode is the positive electrode [1]Cathode is the negative electrode [1]Electrolyteis the substance through which the electricity passes [1] and is broken down [1]

32. (ii) Give two reasons why graphite is a suitable material from which to make the anode and cathode. _____________________________ __________________________ [2](iii) Why is the aluminium oxide dissolved in molten cryolite? __________________________ [2]

33. (ii) Give two reasons why graphite is a suitable material from which to make the anode and cathode.Graphite is a good conductor [1] and is cheaper (than platinum)/inert [1] (iii) Why is the aluminium oxide dissolved in molten cryolite?The molten cryolite lowers the melting point of the aluminium oxide / so reducing costs / saving energy [1] increase conductivity [1]

34. d)(i) Name the products formed a the electrodes during electrolysis and give balanced, ionic equations for the reactions taking place.

35. d)(i) Name the products formed a the electrodes during electrolysis and give balanced, ionic equations for the reactions taking place.

36. (ii) At which electrode is reduction taking place? Explain your answer. _____________________________ _____________________________ __________________________ [3]

37. (ii) At which electrode is reduction taking place? Explain your answer. Reduction is taking place at the cathode [1]. Reduction is the gain of the electrons [1] the aluminium ions are gaining electrons [1]

38. e) Aluminium is an extremely important metal with widespread uses. Give two uses of aluminium and the property on which each use depends. Use ______________________ [1] Property __________________ [2] Use ______________________ [1] Property __________________ [2]

39. e) Aluminium is an extremely important metal with widespread uses. Give two uses of aluminium and the property on which each use depends.Use overhead power cables [1]Property low density / good conductor [1]UseAlloy [1]Property low density (but high strength) [1]Use saucepans [1]Property good thermal conductor [1]

40. f) Aluminium is widely recycled. Suggest two reasons why aluminium metal is recycled. _____________________________ __________________________ [2]

41. f) Aluminium is widely recycled. Suggest two reasons why aluminium metal is recycled. Aluminium is expensive to extract from its ore/cheaper to recycle [1] Bauxite reserves are running out/reduces landfill [1]

42. 2004, Paper 2 6a) The diagram below shows the apparatus used to carry out the electrolysis of molten lithium bromide using graphite electrodes.

43. (i) What is meant by the term electrolysis? _______________________________ _______________________________ [2](ii) During the electrolysis of molten lithium bromide, what would be observed at the anode? _______________________________ _______________________________ [2]

44. (i) What is meant by the term electrolysis? Decomposition/breakdown [1] of compounds using (a direct current of) electricity [1] [2](ii) During the electrolysis of molten lithium bromide, what would be observed at the anode? Anode = brown [1] pungent [1] gas [1] evolved. Any two [2]

45. (iii) Write a balanced ionic equation for the reaction occurring at the anode. _______________________________ [3](iv) Explain as fully as possible why the bulb does not light when the lithium bromide is solid. _______________________________ _______________________________ _______________________________ [3]

46. (iii) Write a balanced ionic equation for the reaction occurring at the anode. Anode = 2Br- → Br2 + 2e- [3](iv) Explain as fully as possible why the bulb does not light when the lithium bromide is solid. Ions [1] cannot move [1] when solid so no flow of current / conduction / circuit incomplete [1] [3]

47. b) The diagram below shows the apparatus used to carry out the electrolysis of dilute sulphuric acid using platinum electrodes. Hydrogen gas and oxygen gas are evolved.

48. (i) Give two reasons why platinum is used for the electrodes. _______________________________ _______________________________ [2](ii) Write a balanced ionic equation for the reaction occurring at the anode. _______________________________ [3]

49. (i) Give two reasons why platinum is used for the electrodes. Conducts electricity [1] inert/does not react with acid [2](ii) Write a balanced ionic equation for the reaction occurring at the anode. Anode = 4OH- → O2 + 2H2O + 4e- [3]

50. (iii) Describe the test you could use to confirm the presence of: Oxygen Gas ________________________ _______________________________ [2] Hydrogen Gas ______________________ _______________________________ [2]