Question

The chemical that is added to reduce the melting point of the reaction mixture during the extraction of aluminium is :

• A. Bauxite
• B. Kaolite
• C. Calamine
• D. Cryolite

Hint:

Cryolite acts as both a solvent and a flux in the metallurgy of Aluminum.

Answer 1

The Correct Option is D

The correct answer to the question is Cryolite. Below is the step-by-step explanation of why Cryolite is used in the extraction process of aluminum.

1. The extraction of aluminum from its ore, bauxite, is typically done using the Hall-Héroult process. This process involves the electrolytic reduction of alumina (Al₂O₃) in a molten mixture.
2. Alumina has a high melting point of about 2072°C. To make the process economically viable, it is necessary to reduce the melting point of the mixture so that the electrolysis can occur at a temperature lower than 1000°C.
3. Cryolite (Na₃AlF₆) is used as a solvent to dissolve alumina. The addition of cryolite decreases the temperature at which the electrolyte becomes molten from 2072°C to around 900–1000°C.
4. This significant reduction in melting point facilitates the electrolytic process of extracting aluminum from alumina, as operating at lower temperatures is more energy-efficient and hence more cost-effective.
5. Consequently, Cryolite is crucial in the aluminum extraction process because it allows electrolytic reduction to occur at manageable temperatures.

Thus, the chemical used to lower the melting point of the reaction mixture during the extraction of aluminum is Cryolite, making it the correct answer.