Plaster of Paris is prepared by heating ___________.

Correct option is A

The correct answer is option (A) gypsum at 373 K.

Here's a breakdown:

• Gypsum: Gypsum is a mineral composed of calcium sulfate dihydrate ($$(CaSO_4, 2H_2O)$$​).
• Heating Process: When gypsum is heated to around 373 K ($$100^0C$$​), it loses some of its water of crystallization.
• Plaster of Paris Formation: This process results in the formation of calcium sulfate hemihydrate ($$CaSO_4, \frac{1}{2}H_2O$$​), which is commonly known as Plaster of Paris.

Chemical Reaction:

$$CaSO_4, 2H_2O (gypsum) → CaSO_4, \frac{1}{2}H_2O (Plaster of Paris) + 1.5H_2O (water)$$​