- Bauxite is the ore containing aluminium oxide (Al₂O₃)
- Cryolite (Na₃AlF₆) lowers melting point from 2072°C to ~950°C — saves huge amounts of energy!
- Cathode half equation: Al³⁺ + 3e⁻ → Al (reduction — aluminium ions gain electrons)
- Anode half equation: 2O²⁻ → O₂ + 4e⁻ (oxidation — oxide ions lose electrons)
- Carbon anodes burn away because O₂ reacts with hot carbon: C + O₂ → CO₂
- Anodes need regular replacement — this is an ongoing cost of the process
- Electrolysis uses HUGE amounts of electricity — very expensive!
- Recycling aluminium saves 95% of the energy vs extracting from ore
- Aluminium is used in aircraft, drinks cans, power cables (low density + good electrical conductor)
- The cathode is made of steel (lined with carbon), the anodes are carbon/graphite
Quick Check: Why is cryolite added to the aluminium oxide in the Hall-Héroult process?
Cryolite lowers the melting point of aluminium oxide from 2072°C to approximately 950°C. This reduces the amount of energy (and therefore cost) needed to keep the mixture molten, making the process economically viable.
This key facts covers Key Facts to Memorise 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 7 of 13 in this topic. Use this key facts 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.