Write the ionic half-equation for the reaction at the cathode during the electrolysis of aluminium oxide.

💡 Al³⁺ ions are reduced at the cathode.

Is the reaction at the cathode oxidation or reduction? Explain your answer using electron transfer.

💡 Think about what happens to the Al³⁺ ion.

During electrolysis of molten aluminium oxide, which ion is attracted to the cathode and why?

💡 Consider the charge on the cathode and the charge on the ion.

Balance the following half-equation for the cathode reaction and add state symbols: Al³⁺ + e⁻ → Al

💡 How many electrons does Al³⁺ need to become a neutral atom?

The electrolysis cell produces 54 g of aluminium. Using the half-equation Al³⁺ + 3e⁻ → Al, calculate the number of moles of electrons transferred at the cathode. (Ar of Al = 27)

💡 First find moles of Al, then use the ratio from the half-equation.

Write the ionic half-equation for the reaction at the anode during the electrolysis of aluminium oxide.

💡 O²⁻ ions are oxidised at the anode. Oxygen gas is produced.

Is the reaction at the anode oxidation or reduction? Explain using oxidation numbers.

💡 What is the oxidation number of oxygen in O²⁻ and in O₂?

The anodes in the aluminium extraction cell are made of carbon. Explain why the anodes need to be replaced regularly.

💡 What happens to carbon when oxygen gas is produced at high temperatures?

Which ion is discharged at the anode during electrolysis of molten aluminium oxide? Why is this ion attracted to the anode?

💡 Consider the charge on the anode.

Complete and balance the overall equation for the electrolysis of aluminium oxide: Al₂O₃ → Al + O₂

💡 Combine the two half-equations. Cancel the electrons.

What physical state is the aluminium produced in the electrolytic cell? Explain why it is in this state.

💡 Consider the temperature of the cell and the melting point of aluminium.

Why must aluminium oxide be molten (not dissolved in water) for electrolysis to work? What does this tell us about the ions in the electrolyte?

💡 Think about what needs to be free to move for electrolysis to occur.

Aluminium oxide is dissolved in molten cryolite before electrolysis. Suggest TWO reasons why cryolite is used.

💡 Consider the melting point of pure Al₂O₃ vs. the mixture, and the economic implications.

A student says: 'The cathode reaction produces solid aluminium which collects at the bottom of the cell.' Identify ONE correct statement and ONE incorrect statement in the student's answer. Explain your reasoning.

💡 Check both the physical state AND the collection method.

Using the two half-equations below, describe what happens at EACH electrode during the industrial extraction of aluminium. Include the type of reaction, the species involved, and what happens to the electrodes over time. Cathode: Al³⁺(l) + 3e⁻ → Al(l) Anode: 2O²⁻(l) → O₂(g) + 4e⁻

💡 Cover: (1) type of reaction, (2) species, (3) electron movement, (4) electrode fate.