Question

In the electrolysis of alumina to obtain aluminium metal, cryolite is added mainly to:

• A. Lower the melting point of alumina
• B. Dissolve the alumina in molten cryolite
• C. Remove impurities from alumina
• D. Increase electrical conductivity

Answer 1

The Correct Option is A

Cryolite (Na₃AlF₆) is essential in the electrolytic extraction of aluminum from alumina (Al₂O₃) due to the following reasons:

1. Melting Point Reduction: Alumina's melting point of approximately 2072°C is drastically reduced to 900°C - 1000°C by the addition of cryolite, improving energy efficiency and cost-effectiveness.

2. Solution Formation: Beyond lowering the melting point, cryolite functions as a solvent for alumina. This dissolution forms a conductive liquid mixture, crucial for effective electrolysis.

3. Electrical Conductivity: The presence of cryolite boosts the solution's electrical conductivity, ensuring efficient current flow for aluminum extraction.

4. Primary Function: The main justification for including cryolite is its ability to "Lower the melting point of alumina."