Extracting Aluminium from Bauxite
Chemistry: Cambridge International GCSE Supplement, topic 9.6.3
Extracting Aluminium from Bauxite
Aluminium is extracted from bauxite by electrolysis using cryolite and carbon anodes; reactions happen at positive and negative electrodes.
Aluminium ore and extraction method
- The main ore of aluminium is bauxite.
- Aluminium is found in bauxite as aluminium oxide (Al2O3).
- Aluminium is extracted by the electrolysis of purified aluminium oxide.
,w_800.png)
Role of cryolite in electrolysis
- Aluminium oxide has a very high melting point.
- Cryolite, a mineral, is mixed with aluminium oxide.
- Cryolite lowers the melting point, saving energy during electrolysis.
,w_800.png)
Carbon anodes in electrolysis
- Electrolysis uses carbon anodes and cathodes.
- Carbon anodes react with oxygen, producing carbon dioxide.
- Carbon anodes wear away and need replacing regularly to maintain the process.
Reactions at the electrodes
- At the cathode (negative electrode), aluminium ions gain electrons:
- Al3+ + 3e- → Al
- At the anode (positive electrode), oxide ions lose electrons and react with carbon:
- 2O2- → O2 + 4e- (oxygen reacts with carbon anode to form CO2)
Test yourself on Extracting Aluminium from Bauxite
What is the primary role of cryolite in the electrolysis of aluminium oxide?