In the electrolytic method for obtaining aluminium from purified bauxite cryolite is generally added to the charge in order to

Options

A. dissolve bauxite and render it conductor of electricity
B. lower the melting point of bauxite
C. minimise the heat loss due to radiation
D. protect aluminium produced from oxygen

Answer

To answer the question about why cryolite is added to the charge in the electrolytic method for obtaining aluminum from purified bauxite, we can break it down into several steps:

### Step-by-Step Solution:

1. **Understanding the Electrolytic Process**: The electrolytic method involves the extraction of aluminum from its ore, bauxite (which primarily consists of aluminum oxide, Al₂O₃). This process requires the ore to be in a molten state to allow for the conduction of electricity.

2. **Role of Cryolite**: Cryolite is a mineral with the chemical formula Na₃AlF₆. It is added to the charge during the electrolytic extraction process.

3. **Lowering the Melting Point**: One of the primary reasons for adding cryolite is to lower the melting point of the aluminum oxide. Pure aluminum oxide has a high melting point (around 2050°C), which makes the process energy-intensive. By adding cryolite, the melting point of the mixture is significantly reduced, making it easier to melt and process.

4. **Increasing Conductivity**: In addition to lowering the melting point, cryolite also increases the electrical conductivity of the molten mixture. This is important because the electrolytic process requires an efficient flow of electricity to facilitate the reduction of aluminum ions to aluminum metal.

5. **Facilitating Dissolution**: Cryolite helps in dissolving the aluminum oxide, rendering it more conductive and allowing for easier extraction of aluminum during the electrolysis process.

### Final Conclusion:
In summary, cryolite is added to the charge in the electrolytic method for obtaining aluminum from purified bauxite primarily to lower the melting point of the mixture and to increase its electrical conductivity, thus enhancing the efficiency of the extraction process.

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