In the metallurgy of aluminium , cryolite is mixed in the molten state because it

Options

A. Increases the mp of alumina
B. Oxidises alumina
C. Reduces alumina
D. Decreases the mp of alumina

Explanation

**Step-by-Step Solution:**

1. **Understanding Cryolite**: Cryolite is a mineral with the chemical formula Na3AlF6. It is used in the metallurgy of aluminum.

2. **Metallurgy of Aluminum**: The primary ore of aluminum is bauxite, which contains aluminum oxide (Al2O3). To extract aluminum from bauxite, a process called electrolytic reduction is used.

3. **High Melting Point of Aluminum Oxide**: Aluminum oxide has a very high melting point of about 2050 °C (or 2323 K). This high melting point makes the extraction process energy-intensive and less efficient.

4. **Role of Cryolite**: Cryolite is mixed with molten aluminum oxide during the electrolytic reduction process. The main reason for adding cryolite is to lower the melting point of aluminum oxide.

5. **Effect of Cryolite on Melting Point**: When cryolite is added, it significantly reduces the melting point of the mixture to about 950 °C (or 1173 K). This reduction in melting point makes the process more energy-efficient.

6. **Conclusion**: Therefore, cryolite is mixed in the molten state during the metallurgy of aluminum primarily to decrease the melting point of aluminum oxide, facilitating the extraction of aluminum.

**Final Answer**: Cryolite is mixed in the molten state in the metallurgy of aluminum to decrease the melting point of aluminum oxide (Al2O3), making the extraction process more efficient.

---