Q. Which of the following corundum and cryolite are important ores ?

Correct Answer: a) Aluminium

Explanation:

Corundum and cryolite are important ores of aluminium.

1. Corundum: It is a crystalline form of aluminium oxide (Al₂O₃) and is a naturally occurring mineral. While it is more commonly known for its gem varieties (like ruby and sapphire), it is also an important source of aluminium.

2. Cryolite: It is a mineral with the chemical formula Na₃AlF₆ (sodium aluminium fluoride). Cryolite was historically used in the electrolytic extraction of aluminium in the Hall-Héroult process, as it lowers the melting point of aluminium oxide, making the extraction process more efficient.