Electroysis

In the process of electrolysis, an eletric current is passed through an electrolyte.

An electrolyte is a liquid or soloution that contains ions and so can conduct electricity.

This causes the ions to move to the electodes, where they form pure elements.

Electrolysis of molten compounds:

Solid Ionic compounds do not conduct electricity as the ions cannot move. To undergo electrolysis they must be molten or dissolved, so the ions are free to move.

When an ionic compoundis molten the postive metal ions are attracted to the cathode, where they will gain electrons to form the pure metal.

The negative non-metal ions are attracted to the anode, where they will lose electrons and become the pure non-metal.

In the electroysis of a soloution, if the non-metal contains oxygen then oxygen gas is formed at the anode

• The OH- (aq) ions formed the ionisation of water are attracted to the anode.
• The OH- (aq) ions lose electrons ti the anode and form oxygen gas.

If the non-metal ion is a halogen, then the halogen gas is formed at the anode.

In the electrolysis of a soloution, if the metal is more reactive than hydrogen then hydrogen gas is formed at the cathode:

• The H+ (aq) ions from the ionisation of water are attracted to the cathode and react with it.
• The H+ (aq) ions gain electrons from the cathode and form hyrodgen gas.
• The metal ions remain in the soloution.

Electrolysis can be used to extract metals from thier ionic compounds.

Electrolysis is used if the metal is more reactive than carbon.

Aluminium is extracted from aluminium oxide by electrolysis.

1. The aluminum oxide is mixed with a substance called cryolite, which lowers the melting point.

2. The mixture is then heated until it is molten.

3. The resulting molten mixture undergoes electroylsis.