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Aluminium is extracted from aluminium oxide by a process called electrolysis.
First of all, aluminium oxide needs to be in molten form to extract the aluminum ions. Aluminium oxide, however, has a high melting point. Therefore, aluminium oxide is dissolved in molten cryolite. Cryolite is a form of an aluminium compound that has a lower melting point that aluminium oxide.
The steel case, used in electrolysis, is coated by graphite. Graphite is a form of carbon and acts at the negative cathode.
The positive anodes are also made of graphite but are immersed in the molten cryolite solution.
When electricity flows,
Aluminium ions, from the aluminium oxide, are formed at the negative cathode and then sink at the bottom because they are heavier than the cryolite solution. Then, this aluminium is collected in liquid form
On the other hand, the oxygen, from the aluminium oxide, forms at the positive anode and reacts with the carbon of the graphite to form carbon dioxide CO2.
Edwinnyongesa8 answered the question on April 26, 2018 at 11:13
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