In Hall's process of electrolytic reduction of alumina . Name the Cathode .

Explanation

Bauxite is the chief ore aluminium . The extraction of aluminium from bauxite involves two steps :
(i) The conversion of Bauxite into Alumina involves the following steps:
Bauxite ore is finely ground and heated under pressure with a solution of concentrated caustic soda at `150^@C ` to obtain sodium meta aluminate.
One diluting sodium meta aluminate with water , a precipitate of aluminium hydroxide is formed .
The precipitate is flitered , washed , dried and ignited at `100^@C` to get alumina.
(ii) Aluminium is produced by the electrolytic reduction of fused alumina `(Al_2O_3)` in the electrolytic cell.
Cathode : Iron tank linked with graphite
Andon : A bunch of graphite rods suspended in molten electrolyte.
Electrolyte :
Pure alumina + molten cryolite + fluorspar
`2Al(OH)_3overset(1000^@C)rarrAl_2O_3+3H_2O`
Temperature : `900-950^@C`
Voltage used : 5 - 6 V
Overal reaction :
`2Al_2O_3rarr4 Al + 3O_2 uarr`