Question

Given below are two statements:
Assertion (A): Gypsum has lower density than anhydrite.
Reason (R): Hydrated minerals tend to expand many times the original volume of the anhydrous minerals.

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is not the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Gypsum is hydrated calcium sulphate, while anhydrite is anhydrous calcium sulphate.

Answer 1

The Correct Option is A

Concept:
Gypsum is hydrated calcium sulphate, while anhydrite is anhydrous calcium sulphate.

Step 1: Compare minerals.
Gypsum: \[ CaSO_4\cdot 2H_2O \] Anhydrite: \[ CaSO_4 \]

Step 2: Effect of hydration.
Hydration increases volume because water molecules enter the crystal structure. \[ \text{Volume increases} \Rightarrow \text{density decreases} \]

Step 3: Final conclusion.
Gypsum has lower density than anhydrite, and the reason correctly explains it. \[ \therefore \text{Correct Answer is (A)} \]