C6.1.8 Extracting Aluminium

Question 1

Aluminium

Answer 1

Exists naturally mainly as aluminium oxide - Al2O3
Found in ore called bauxite
Aluminium more reactive than carbon:
So unlike iron + copper must be extracted from its ore = electrolysis

Question 2

When les electrolysis work?

Answer 2

If a compound is in a solution of molten
- aluminium oxide doesn’t dissolve in water + melting point is high
= too expensive to melt + requires too much energy

Question 3

Main uses of aluminium

Answer 3

• drinking cans
• Tin-foil
• window frames
• aeroplanes

Question 4

Two methods to extract

Answer 4

Heating with carbon

Electrolysis

Question 5

How is aluminium oxide electrolysed?

Answer 5

Melting point over 2000
Dissolved in molten cryolite
Cryolite much lower melting point than aluminium oxide
So
Allows electrolysis to happen at 950
Molten mixture = aluminium oxide + cryolite contained in huge electrolysis cell

Question 6

Half equations happen during electrolysis

Answer 6

Cathode: Al3+ + 3e- —> Al
Anode: 2O2- —> O2 + 4e-
Overall = 2Al2O3 —> 4Al + 3O2