The function of fluorspar in the electrolytic reduction of alumnia dissolved in fused cryotile `(Na_(3)AlF_(6))` is:

Options

A. as a catalyst
B. to lower the temperature of the melt and to make the fused mixture very conducting
C. to decrease the rate of oxidation of carbon at the anode
D. none of the above

Answer

To solve the question regarding the function of fluorspar in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆), we can break it down into the following steps:

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Fluorspar is chemically known as calcium fluoride (CaF₂).
- Cryolite is sodium aluminum fluoride (Na₃AlF₆).

2. **Understand the Role of Cryolite**:
- Cryolite is used in the electrolytic reduction process primarily to lower the melting point of alumina (Al₂O₃). This is important because it allows the process to occur at a lower temperature, which saves energy and improves efficiency.

3. **Understand the Role of Fluorspar**:
- Fluorspar (CaF₂) serves to increase the fluidity of the molten mixture. By enhancing fluidity, it allows for better movement of the molten aluminum and other components within the electrolytic cell.

4. **Effect of Increased Fluidity**:
- The increased fluidity of the molten mass ensures that the liberated aluminum metal can easily sink to the bottom of the electrolytic cell. This is crucial for the efficient collection of aluminum during the electrolysis process.

5. **Conductivity of the Mixture**:
- The combination of cryolite and fluorspar also contributes to making the fused mixture more conductive. This is essential for the passage of electric current through the mixture, facilitating the electrolytic reduction process.

6. **Conclusion**:
- Therefore, the function of fluorspar in this process is twofold: it increases the fluidity of the melt and contributes to the overall conductivity of the fused mixture, which is vital for the efficient reduction of alumina to aluminum.

### Final Answer:
The function of fluorspar in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆) is to **increase the fluidity of the mass and make the fused mixture very conductive**.

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