Question

electrolysis of alumina is done write chemical equation

Answer 1

HEY DEAR YOUR ANSWER IS HERE
lectrolysis of the alumina/cryolite solution gives aluminium at the cathode and oxygen at the anode.

Al3+  +  3e-       Al (aluminium metal at the (-)cathode)
2O2-  -  4e-       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       aluminium + oxygen
2Al23+O32-(l)                 4Al(l)   +     3O2(g)