Why is plaster of Paris stored away from moisture?
Answer and explanation
Correct answer: Because it can gradually set on absorbing moisture
The governing concept is the hydration and setting of plaster of Paris (calcium sulphate hemihydrate). It reacts with absorbed water to form gypsum, calcium sulphate dihydrate, which is a hard solid: 2CaSO4·1/2H2O + 3H2O → 2CaSO4·2H2O. Therefore, moisture may make the powder set before it is required. Option D is correct; the other options describe no such storage-related reaction.
Frequently asked questions
What is the correct answer to this question?
Because it can gradually set on absorbing moisture
Why is this the correct answer?
The governing concept is the hydration and setting of plaster of Paris (calcium sulphate hemihydrate). It reacts with absorbed water to form gypsum, calcium sulphate dihydrate, which is a hard solid: 2CaSO4·1/2H2O + 3H2O → 2CaSO4·2H2O. Therefore, moisture may make the powder set before it is required. Option D is correct; the other options describe no such storage-related reaction.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
