| Electrode | Process | Half equation | What happens |
|---|---|---|---|
| CATHODE (−) | Reduction — gain of electrons | Al³⁺ + 3e⁻ → Al |
Aluminium ions gain 3 electrons → molten aluminium metal sinks to the bottom |
| ANODE (+) | Oxidation — loss of electrons | 2O²⁻ → O₂ + 4e⁻ |
Oxide ions lose electrons → oxygen gas; oxygen reacts with hot carbon: C + O₂ → CO₂ |
Overall equation: 2Al₂O₃ → 4Al + 3O₂
This requires electrical energy — it is NOT a spontaneous reaction.
This comparison covers Half Equations — Must Know! within Electrolysis of Aluminium for GCSE Chemistry. Revise Electrolysis of Aluminium in Electrolysis for GCSE Chemistry with 21 exam-style questions and 14 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 4 of 13 in this topic. Use this comparison to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Electrolysis of Aluminium
Why is aluminium extracted by electrolysis rather than by reduction with carbon?
Explain why aluminium is extracted by electrolysis rather than by reduction with carbon.
Quick recall flashcards
Why do the carbon anodes need replacing regularly?
At 950°C, the oxygen produced at the anode reacts with the hot carbon: C + O₂ → CO₂. The carbon is gradually burned away, so the anodes must be replaced periodically.
What does OIL RIG stand for?
Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
At the Anode = Oxidation (loss). At the Cathode = Reduction (gain).