Question

Write the cathode / anode / & total net reaction of aluminium.

Answer 1

Answer:

The steel container is coated with carbon (graphite) and this is the negative electrode (cathode).

Electrolysis of the alumina/cryolite solution gives aluminium at the cathode and oxygen at the anode.

Al3+ + 3e- arrow Al (aluminium metal at the (-)cathode)

2O2- - 4e- arrow O2 (oxygen gas at the (+)anode)

Aluminium is more dense than the alumina/cryolite solution, and so falls to the bottom of the cell where it can be tapped off as pure liquid metal.

The overall reaction is

aluminium oxide arrow aluminium + oxygen

2Al23+O32-(l) arrow 4Al(l) + 3O2(g)

Oxygen is discharged at the positive carbon (graphite) anode.Oxygen reacts with the carbon anode to form carbon dioxide gas.

carbon + oxygen arrow carbon dioxide

C(s) + O2(g) arrow CO2(g)

The carbon anode slowly reacts to make carbon dioxide and needs to be replaced regularly.