Electrolysis

Electrolysis -  the breaking down of a sustance (containing ions) using electricity.

Cathode - the negative electrode in electrolysis

Anode - the postive electrode in electrolysis

Brine - water containing lots of salt

Half equations - an equation that describes reduction or oxidation

Electrolyte - a liquid containing free moving ions, which is broken down in electrolysis

Molten substance - substance liquified by heat

Inert - unreactive

2Cl     Cl    2e

2Br     Br    2e           Oxidaiton 

2F      F     2e

Ca      2e     Ca

Al       3e      Al          Reduction

H        2e     H

Oxidation - the loss of electrons

Reduction - the gain of electrons

A way to remember it is OIL RIG, which is: 

O xidation

I s 

L oss

R eduction 

I s 

G ain 

They each say 'of elctrons' at the end.

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Half eqautions

(ox) + 2Cl      Cl  +  Cl  +  2e

(red) - Cu   +  2e     Cu

In electrolyisis the negatively charged ions go towards the positive electrode (anode, +), they receive electrons and are reduced. The postively charged ions go towards the negative electrode (cathode, -), they receive electrons which are oxidised.

1. Bauxite which contains aluminium oxide is mined from the earth

2. The bauxite contains lota of impurities which are then seperated from the aluminium oxide.

3. The pure aluminium oxide is then melted

4. Cryolite is mixed with the molten aluminium oxide to lower the melting point, which reduces the amount of energy required

5. The mixture of cryolite and aluminium oxide is electrolysed

6. Oxygen ions move to the postive electrode and loses electrons. And the aluminium ions move to the negative electrode which lines the cell

7. The aluminium ion gains 3 electrons and becomes aluminium

8. The oxygen reacts with the carbon in the electrode and makes carbon dioxide gas

9. Molten aluminium siphoned off

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Half equations

(ox) + 2Cl     Cl   + 2e

(red) + Cu   + 2e      Cu