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Secondary revision · Chemistry Form 3

Electricity and Chemistry

Question 1 of 26 Grade: Form 3
Q1
Graphite is often used as an electrode in the electrolysis of solutions. Which particles are involved in the conduction of electricity by graphite? A) Electrons only B) Negative ions only C) Positive ions and electrons D) Positive ions and negative ions
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About this topic

This topic, also known as Electrochemistry, explores the relationship between electrical energy and chemical reactions as outlined in the Zambian Competence-Based Curriculum. You will learn to distinguish between conductors and non-conductors, understand electrolysis of molten and aqueous compounds, and investigate the industrial applications of electrolysis, such as metal extraction and electroplating. This knowledge links to Zambia's mining industry and technology. ECZ examinations commonly include questions on predicting products of electrolysis and drawing cell setups. Mastering this topic equips you with the principles behind batteries, corrosion, and important industrial chemical processes, which are key areas for exam revision and practical assessment.

What you'll practise (26 questions)

  1. Graphite is often used as an electrode in the electrolysis of solutions. Which particles are involved in the conduction of electricity by graphite? A) Electrons only B) Negative ions only C) Positive ions and electrons D) Positive ions and negative ions
  2. Aqueous copper (II) sulphate is electrolysed using copper electrodes. The current is constant and the anode (positive electrode) is weighed at regular intervals. Which graph is obtained when the mass of the anode is plotted against time?
  3. The relative atomic mass of element Q is 208. When a current of 0.5A was passed through a fused bromide of Q for 16 minutes 5 seconds, 0.26g of Q was deposited at the cathode. Deduce the formula for the Q ion and for the sulphate of Q.
  4. Concentrated sodium chloride solution (Brine) was electrolysed using the apparatus below. Which of the following correctly represents P, Q and the pH of the solution?
  5. The diagram shows an application of electrolysis in industry. The above application is best known as... A) anodization B) deposition C) electroplating D) galvanizing
  6. In which circuit does the bulb light?
  7. What is observed during the electrolysis of aqueous copper (II) sulphate using carbon electrodes? A) A pink solid is deposited on the anode B) Bubbles of a colourless gas are produced at the negative electrode C) The colour of the solution fades D) The negative electrode becomes smaller
  8. A current of 0.5 amperes was passed for 2,400 seconds through colorimeters in series. What quantity of electricity was used?
  9. Write ionic equations for reactions occurring at the two anodes in the electrolysis of dilute sodium hydroxide and molten potassium iodide.
  10. How many moles of electrons were passed through each electrolyte?
  11. What mass of product is liberated at the cathode in the potassium iodide voltameter?
  12. State any two applications of electrolysis.
  13. In the purification of copper by electrolysis, state the names of: (i) the electrolyte (ii) the anode (iii) the cathode
  14. Write ionic equations for the reactions taking place at the electrodes during the purification of copper.
  15. A current of 5A is passed through the electrolyte for half an hour during the purification of copper. What mass of pure copper is obtained from the impure copper during the stated time? (1F = 96,500C)
  16. A current of 50A is passed in the electrolyte for 1 hour. Calculate the mass of aluminium that will be produced. (1F = 1 mole of electrons = 96,500C)
  17. Lead (II) bromide was electrolysed using inert electrodes as shown in the circuit diagram. Why does the lamp in the circuit light up only when the lead (II) bromide is melted?
  18. If a copper ring has to be silver plated, the best arrangement is...
  19. Which element needs the smallest number of electrons for one mole of atoms to be liberated during electrolysis?
  20. The diagram below shows the apparatus used in the purification of impure copper by electrolysis in an industry. Which equation represents the electrode reaction on plate B (cathode)?
  21. The diagram below shows the electrolysis of dilute sulphuric acid. What is gas X?
  22. The diagram below shows the electrolysis of aqueous copper (II) sulphate using copper electrodes. Which graph shows how the mass of the cathode changes during electrolysis?
  23. An element X has a relative atomic mass of 88. When a current of 0.5 amps was passed through the fused chloride of X for 32 minutes 10 seconds, 0.44g of X was deposited at the cathode. What is the number of Faradays required to liberate 1 mole of X? (1 Faraday = 96500 coulombs)
  24. The diagram shows the electrolysis of aqueous magnesium chloride and molten magnesium chloride. In the diagram, which substance has both positive ions and mobile electrons?
  25. An iron nail is to be electroplated with silver. Which entries in the table are correct?
  26. Two molten salts, magnesium chloride and titanium chloride (TiClₓ) are electrolysed using the same current. If 4.8g of Mg and also 4.8g of Ti are produced at their respective cathode electrodes, what is the charge on the titanium ion?

Answer each question above to see the correct answer and a full explanation.