Electrolysis of aluminium oxide

How are metals less reactive than carbon extracted

Extracted By reduction with carbon

How are metals more reactive than carbon extracted

Extracted using electrolysis

How is aluminium extracted

Extracted from the compound aluminium oxide by electrolysis

Aluminium Oxide formula

Al2O3

What does aluminium oxide contain

The aluminium ion (Al3+)

The oxide ion (O2-)

Melting point of aluminium oxide

Very high

Around 2000C

First stage of electrolysis of aluminium oxide

It is mixed with cryolite, which lowers the melting point.

This reduces amount of energy needed and saves energy

Second stage of electrolysis of aluminium oxide

We apply an electric current to the aluminium oxide (electrolysis)

What are the anode and cathode made from

Graphite (a form of carbon)

Why is graphite used

Is a very good conductor of electricity

Has a very high melting point, so can be used at high temperatures without melting

Where do the aluminium ions go

Aluminium Ions Are attracted to the cathode.

Each ion gains three electrons and forms an aluminium atom

Half equation of aluminium in reduction

Al (3+) + 3e- ——> Al

Reduction

What happens to the oxide ions

The Oxide Ions Are attracted to the anode

Each oxide ion loses two electrons to form an oxygen atom

Half equation of oxide ions being oxidised

O(2-) ——> O + 2e-

Oxidation

What else happens to oxygen atoms at anode

They pair up to form the oxygen molecule O2

What does this mean

We must double the oxidation reactions

2O(2-) ——> O2 + 4e-

What must happen to the anode

Must be replaced regularly

Why must anode be replaced regularly

The oxygen molecules produced at the anode react with the graphite (carbon) and form carbon dioxide gas.

Cost of electrolysis

Very expensive

Why is electrolysis very expensive

Melting the compounds such as aluminium oxide requires a great deal of energy.

A lot of energy is required to produce the electric current