chemical reactions - electrolysis of aluminium oxide

Question 1

how is aluminium extracted from its compound?

Answer 1

by electrolysis

Question 2

what is aluminium made up of?

Answer 2

aluminium ion 3 plus
oxide ion 2 minus

it also has a very high melting point

Question 3

what are the first 2 steps to extracting aluminium from its compound?

Answer 3

1. aluminium oxide is mixed with cryolite which lowers the melting point. this reduces the energy needed and saves money
2. electric current is applied to the molten aluminium oxide

Question 4

In aluminium oxide, what happens to the 3 plus aluminium ions?

Answer 4

they are attracted to the negative left rode, the cathode, where they will gain 3 electrons to form aluminium atoms. this is a reduction reaction.

Al 3 plus + 3 electrons minus -> Al

Question 5

What happens to the 2 minus oxide ions during electrolysis?

Answer 5

the ions are attracted to the positive electrode, the anode, where they lose 2 electrons. this is an oxidation reaction

2O 2 minus -> O + 4e-
2O2 minus - e- -> O

oxygen atoms pair up to form molecules

Question 6

How often should anode be replaced and why?

Answer 6

regularly as the oxygen molecules produced at the anode react with the graphite electrode, forming carbon dioxide gas.

C + O2 -> CO2

Question 7

why is electrolysis expensive?

Answer 7

• melting compounds such as aluminium oxide requires a great deal of energy
• a lot of energy is required to provide an electric current