Question 1: Define the term 'electrolysis' and explain its role in aluminium extraction.

Answer: Electrolysis is a chemical process where an electric current is used to cause a non-spontaneous chemical reaction. In aluminium extraction, it is used to decompose aluminium oxide into aluminium metal and oxygen gas.

Question 2: What is the name of the process used to extract aluminium from its ore, and what electrolyte is used?

Answer: The process is called the Hall-Héroult process, and the electrolyte used is molten aluminium oxide (alumina) dissolved in cryolite.

Question 3: Explain why cryolite is added to aluminium oxide during electrolysis.

Answer: Cryolite lowers the melting point of aluminium oxide, making electrolysis more energy-efficient and easier to conduct.

Question 1: Calculate the amount of electric charge (in Coulombs) required to produce 10 grams of aluminium, given that the electrolysis of aluminium oxide involves 3 moles of electrons per mole of aluminium. (Atomic mass of Al = 27 g/mol, 1 Faraday = 96485 C).

Answer: First, calculate moles of aluminium: 10 g / 27 g/mol ≈ 0.3704 mol. Since 3 mol of electrons are needed per mol of aluminium: 0.3704 mol × 3 ≈ 1.1112 mol of electrons. Total charge: 1.1112 mol × 96485 C/mol ≈ 107,170 C.

Question 2: If the electrolysis cell operates at a constant current of 1000 A, how long (in hours) will it take to produce 5 grams of aluminium?

Answer: Calculate moles of aluminium: 5 g / 27 g/mol ≈ 0.1852 mol. Electrons needed: 0.1852 mol × 3 ≈ 0.5556 mol. Charge required: 0.5556 mol × 96485 C/mol ≈ 53,440 C. Time = Charge / Current = 53,440 C / 1000 A ≈ 53.44 seconds ≈ 0.015 hours.

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

Answer: Use of protective gloves and goggles to prevent contact with molten cryolite and aluminium; ensuring proper ventilation to avoid inhalation of fumes.

Question 2: Describe one major practical challenge of maintaining the electrolysis process for aluminium extraction.

Answer: Maintaining a high temperature to keep the electrolyte molten while preventing damage to equipment and managing the flow of current efficiently.

Question 1: During an industrial electrolysis process, it was observed that only 80% of the theoretical amount of aluminium was produced from a given amount of electricity. What might be some reasons for this inefficiency?

Answer: Possible reasons include energy losses as heat, incomplete electrolysis, impurities in the electrolyte, or equipment inefficiencies causing some current to be wasted.

Question 1: Explain why aluminium is a popular material in the aerospace industry.

Answer: Aluminium is lightweight, strong, resistant to corrosion, and has good thermal and electrical conductivity, making it ideal for aerospace applications.

Question 2: Describe one environmental concern associated with aluminium extraction via electrolysis.

Answer: The process consumes a large amount of energy, often from non-renewable sources, leading to high carbon emissions; also, the disposal of fluoride by-products can cause environmental pollution.