Q22.28P - Chemistry: Molecular Nature Of Matter And Change

Question

Why is cryolite used in the electrolysis of aluminum oxide?

Step-by-Step Solution

Answer

Cryolite( ${\mathrm{Na}}_3{\mathrm{AlF}}_6$) is used in the electrolysis of aluminum oxide because cryolite helps to extract aluminum profitably.

Step 1: Cryolite

The compound cryolite is sodium aliminium fluoride $\mathbf{\left(}{\mathbf{Na}}_3{\mathbf{AlF}}_6\mathbf{\right)}$. It is added to bauxite in aluminum smelting.

Step 2: Explanation

- The high melting point of aluminum oxide is ${\text{2030}}^{\text{°}}\text{C}$ . The Hall-Héroult process makes    

    it difficult to refine aluminum.

- When cryolite is added, the melting point of the mixture becomes ${\text{1000}}^{\text{°}}\text{C}$ .

- Cryolite can also act as a solvent. It increases the conductivity of the solution of molten  

   bauxite.

-Therefore, cryolite helps to extract aluminum profitably.