Question

With respect to the Hall Heroult process, justify the following:

Graphite anodes are continuously replaced during the electrolysis.

Answer 1

The graphite anodes are continuously replaced during the electrolysis because:

1. The oxygen evolved at the anode escapes as a gas or reacts with the carbon anode.
2. The carbon anode is thus oxidized to carbon monoxide which either burns giving carbon dioxide or escapes out through an outlet.
   \[\ce{2C + O2 -> 2CO}\]
   \[\ce{2CO + O2 -> 2CO2}\]