Question

Assertion: Gypsum upon strong heating forms Plaster of Paris.

Reason: Upon strong heating, Gypsum loses molecules of water of crystallization partially.

• A. both assertion and reason are correct and the reason is the correct explanation for assertion
• B. both assertion and reason are correct but the reason is not the correct explanation for assertion.
• C. the assertion is correct but the reason is incorrect.
• D. the assertion is incorrect but the reason is correct.

Answer 1

The correct option is A

both assertion and reason are correct and the reason is the correct explanation for assertion

Explanation for the assertion statement:-

1. Plaster of Paris(POP) is a hydrated calcium sulphate $\left({\mathrm{CaSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\right)$having half molecule of water.
2. It is also referred to as Gypsum plaster.
3. Plaster of Paris is manufactured by heating Gypsum at nearly 373 K.
4. Gypsum is dihydrated calcium sulphate.

Explanation of reason statement:-

Upon heating, the molecules of water present in the crystals of Gypsum are converted into water vapors and they escape out.

The reaction involved is given as:-

$\underset{\mathrm{Gypsum}}{{\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}}\stackrel{373\mathrm{K}}{\to }\underset{\mathrm{Plaster}\mathrm{of}\mathrm{Paris}}{{\mathrm{CaSO}}_4.\frac{1}{2}{\mathrm{H}}_2\mathrm{O}}+1\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$

Thus, both Assertion and Reason are correct and the reason is the correct explanation for the assertion.

Hence, the correct option is (A).