Question

In order to obtain one tonne of aluminum, the following inputs are required: four tonnes of bauxite, $150Kg$ of Sodium hydroxide, and $600Kg$ of graphite. The aluminum compound in bauxite is aluminum oxide and the main impurity is iron $\left(III\right)$ oxide. Aluminum is obtained by the electrolysis of aluminum oxide dissolved in cryolite.

Why is so much graphite required for this electrolytic process?

Answer 1

• The electrolysis of fused Alumina includes cathode as the iron tank lined with carbon(graphite) and anode as a number of carbon rods which is dipped in the fused electrolyte.
• The oxygen liberated during the process of electrolysis oxidized the carbon at the anode.
• The oxidation of the carbon results in the formation of Carbon dioxide and Carbon monoxide.
• So anode needs to be replaced during the process. The reaction is,
• $$\begin{gathered} Anode:\underset{Carbon}{C\left(s\right)}+O^{2-}\to \underset{Carbonmonoxide}{CO\left(g\right)}+2e^{-} \\ C\left(s\right)+2O^{2-}\to \underset{Carbondioxide}{C{O}_2\left(g\right)}+4e^{-} \end{gathered}$$

Because the reaction or oxidation of carbon with oxygen liberated at the anode needs to be replaced hence so many graphite or carbon rods are needed during the electrolysis process.