Question

Which is not a mineral of aluminium?
A.Anhydrite
B.Bauxite
C.Corundum
D.Diaspore

Answer 1

Hint: Few elements are found in nature in the Free State. Many are found in the form of oxides, sulphates, phosphates, carbonates and silicates. The compound of a metal found in nature is called mineral. The minerals from which the metal can be extracted are called ores. Aluminium is also extracted from ores.

Complete step by step answer:
Anhydrite is a mineral with chemical formula $CaS{O_4}$. It is anhydrous calcium sulphate. It is clear from the chemical formula that it is a mineral of calcium.
Bauxite is a mineral of aluminium as it has a chemical formula$A{l_2}{O_3}.2{H_2}O$. It contains two water molecules. It is oxide of aluminium. It is generally used to extract aluminium.
Corundum has a chemical formula $A{l_2}{O_3}$. It is also an oxide of aluminium so it is also a mineral of aluminium.
Diaspore has a chemical formula $A{l_2}{O_3}.{H_2}O$. It contains one water molecule. It is also an oxide of aluminium so it is also a mineral of aluminium.
Hence the answer is anhydrite as it is not a mineral of aluminium.

The correct answer is option A.

Note:
Aluminium is obtained from bauxite by electrolysis process. It involves three steps-
First, bauxite is purified using different methods which depends on the impurities present in the ore. Bayer’s method or Hall’s method is used for red bauxite containing iron oxide and silica as impurities. Serpeck’s method is used for white bauxite containing silica as impurity.
The purified aluminium oxide is then mixed with cryolite or fluorspar (to lower the melting point) and electrolyzed. Aluminium metal is deposited at the cathode.