Electrolysis is used to remove aluminium from its ore, bauxite. This is because when it is found, it is usually in a compound – aluminium oxide. Therefore, the aluminium needs to be extracted using electrolysis.
Since aluminium oxide has a very high melting point, melting it would cost a lot of money. Instead, it is dissolved in molten cryolite, which is a less common ore of aluminium. This lowers the temperature and so it makes it much cheaper and easier to use.
Aluminium forms at the negative electrode and oxygen forms at the positive electrode:
Negative electrode: Al3+ + 3e- Al
Positive electrode: 2O2- O2 + 4e-
