Question 1: Define electrolysis and explain its role in extracting aluminium from aluminium oxide.

Answer: Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous chemical reaction. In aluminium extraction, electrolysis breaks down aluminium oxide into aluminium metal and oxygen gas.

Question 2: Describe the purpose of the cryolite (Na₃AlF₆) in the industrial process of aluminium extraction.

Answer: Cryolite lowers the melting point of aluminium oxide, making electrolysis more energy-efficient and facilitating the process.

Question 3: Explain why aluminium oxide must be melted before electrolysis can occur.

Answer: Electrolysis requires the substance to be in a molten state to allow ions to move freely and conduct electricity.

Question 1: Calculate the amount of electric charge (in coulombs) required to produce 27 grams of aluminium metal during electrolysis. (Atomic mass of Al = 27 g/mol; 3 electrons are needed to produce 1 atom of Al).

Answer: 3,000 coulombs

Question 2: If the current used in an industrial electrolytic cell is 2000 A, how long (in hours) does it take to produce 54 grams of aluminium?

Answer: 4.5 hours

Question 1: Identify three safety precautions that must be taken during the industrial electrolysis of aluminium.

Answer: Proper insulation of electrical equipment, handling of molten substances with protective gear, and ensuring adequate ventilation to prevent gas build-up.

Question 2: Suggest one way the process of aluminium extraction could be made more energy-efficient.

Answer: Using alternative, lower-temperature electrolytes or renewable energy sources to reduce energy consumption.

Question 1: A factory reports that 150,000 kWh of energy is consumed to produce 50 tonnes of aluminium annually. Calculate the average energy consumption per tonne of aluminium.

Answer: 3,000 kWh per tonne

Question 2: Discuss one environmental concern associated with the electrolysis process for aluminium extraction and suggest a possible mitigation strategy.

Answer: The process releases perfluorocarbons which contribute to greenhouse gases. Using alternative, more environmentally friendly electrolytes or capturing and recycling gases can mitigate environmental impact.

Question 1: Explain the role of electricity in the extraction of aluminium and outline the main steps involved in the process. (6 marks)

Answer: Electricity provides the energy needed to break down aluminium oxide into aluminium metal and oxygen gas via electrolysis. The main steps include melting aluminium oxide mixed with cryolite, inserting electrodes into the molten mixture, passing an electric current to cause ion migration, reduction of aluminium ions at the cathode to form aluminium metal, and oxidation of oxide ions at the anode to produce oxygen gas.