UPSC NDA I 2021 General Ability Solved Paper

The correct answer is Mixing water to Plaster of Paris.
Key Points
- When plaster of Paris is mixed with water, it gets converted into gypsum.
∘CaSO4⋅‌

1

2

H2O+H2O→CaSO4⋅2H2O,
Hence it doesn't give hydrogen gas. (Plaster of Paris) (Water) ‌‌ (Gypsum)
- While heating of Gypsum at 373 K results in Plaster of Paris.