Question

Kaolin mainly consists of

• A. Magnesium silicate
• B. Aluminium silicate
• C. Magnesium phosphate
• D. Aluminium phosphate

Hint:

Kaolin is composed mainly of aluminium silicate and is commonly used in ceramics and pharmaceuticals.

Answer 1

The Correct Option is B

Step 1: Understanding the composition of Kaolin.
Kaolin, also known as China clay, is a naturally occurring clay mineral primarily composed of aluminium silicate. It is widely used in ceramics, medicine, and as a food additive.
Step 2: Analyzing the options.
(A) Magnesium silicate: This is incorrect as kaolin is not composed of magnesium silicate.
(B) Aluminium silicate: Correct — Kaolin is primarily made of aluminium silicate, which gives it its characteristic properties.
(C) Magnesium phosphate: This is incorrect as kaolin does not contain magnesium phosphate.
(D) Aluminium phosphate: Kaolin does not consist of aluminium phosphate.
Step 3: Conclusion.
The correct answer is (B) Aluminium silicate as kaolin is primarily composed of aluminium silicate.

Answer 2

We can approach this through the basic chemistry of clay minerals, comparing silicate versus phosphate compositions.

1. Magnesium silicate: Magnesium silicate is the chemical basis of talc, a different clay-type mineral used in cosmetics and as a lubricant, not the composition of kaolin.
2. Aluminium silicate: Kaolin (China clay) is a hydrated aluminium silicate, chemically represented approximately as Al2Si2O5(OH)4, formed from the weathering of feldspar-rich rocks; this matches kaolin's known mineral composition.
3. Magnesium phosphate: This is an entirely different class of compound (a phosphate salt), unrelated to clay minerals and not a constituent of kaolin.
4. Aluminium phosphate: Similarly, this phosphate compound is chemically distinct from the aluminosilicate mineral structure that defines kaolin.

Kaolin's defining mineral, kaolinite, is specifically a hydrated aluminium silicate, distinguishing it from both magnesium silicate (talc) and the two phosphate compounds listed.

Therefore, the correct answer is Aluminium silicate.