Question 1: Define electrolysis in the context of molten substances.

Answer: Electrolysis is a chemical process where electrical energy is used to break down a molten ionic compound into its elements.

Question 2: Explain why molten electrolysis requires the substance to be in a molten state rather than in solution.

Answer: Because ions need to be free to move; in solution, ions are already mobile, but in molten state, the ionic bonds are broken, allowing ions to conduct electricity and be separated.

Question 3: Describe the mechanism of ion migration during electrolysis of a molten salt.

Answer: Positive ions migrate towards the cathode to gain electrons and be reduced, while negative ions migrate towards the anode to lose electrons and be oxidised.

Question 1: During electrolysis of aluminium oxide (Al₂O₃), 96,000 Coulombs of charge are passed through the cell. How many moles of aluminium are produced? (Molar charge of aluminium ion, Al³⁺, is 3 mol of electrons per mol of Al).

Answer: Moles of Al = Total charge / (Number of electrons per mole × Faraday's constant) = 96,000 C / (3 × 96485 C/mol) ≈ 0.33 mol

Question 2: If the electrolysis of molten sodium chloride produces 1.5 grams of sodium metal, calculate the total charge passed, given that the molar mass of sodium is 23 g/mol and each Na atom requires 1 electron to be reduced.

Answer: Total moles of Na = 1.5 g / 23 g/mol ≈ 0.065 mol; Total charge = moles × number of electrons × Faraday’s constant = 0.065 mol × 1 × 96485 C/mol ≈ 6281 C

Question 1: Describe a safe procedure for setting up a molten electrolysis experiment, including safety precautions.

Answer: Set up the apparatus in a well-ventilated area, wear heat-resistant gloves and eye protection, ensure the power supply is off before connecting electrodes, handle molten substances with tongs, and keep flammable materials away from the high-temperature setup.

Question 2: Identify three variables that could affect the efficiency of molten electrolysis and explain how they influence the process.

Answer: Variables include temperature (higher temperatures improve ion mobility), electrode material (affects durability and reaction efficiency), and voltage applied (higher voltage can increase current but may cause unwanted side reactions).

Question 1: A student electrolyses a molten salt and collects 2.5 grams of a metal at the cathode after passing 20,000 Coulombs of charge. The molar mass of the metal is 55.8 g/mol, and it requires 2 electrons to reduce each ion. Calculate the number of moles of metal produced and discuss whether the data suggests complete electrolysis.

Answer: Moles of metal = 2.5 g / 55.8 g/mol ≈ 0.045 mol; Theoretical charge for 0.045 mol = 0.045 mol × 2 × 96485 C/mol ≈ 8699 C; Since only 20,000 C was passed, the electrolysis was incomplete, as less than the theoretical charge was used.

Question 1: Explain why aluminium is extracted from its ore using molten electrolysis instead of reduction with carbon. (6 marks)

Answer: Aluminium oxide cannot be reduced by carbon because it reacts with carbon at high temperatures to form aluminium carbide, which contaminates the metal. Molten electrolysis allows for the direct extraction of pure aluminium by breaking down aluminium oxide into aluminium metal and oxygen gas without contamination.

Question 1: Discuss the role of molten electrolysis in the production of aluminium and its importance in modern manufacturing.

Answer: Molten electrolysis is used to extract aluminium from bauxite ore as it produces pure aluminium efficiently. This process is vital for manufacturing aircraft, packaging, and construction materials due to aluminium's lightweight and durable properties.