Correct option is C
The correct answer is: (C) CaSO₄ ∙ ½H₂O
Explanation:
- Plaster of Paris is made by heating gypsum (CaSO₄ · 2H₂O) to remove water molecules.
- Gypsum is chemically calcium sulfate dihydrate (CaSO₄ · 2H₂O).
- Upon heating, Plaster of Paris is formed, which has the chemical formula CaSO₄ · ½H₂O.
- This means that for every molecule of calcium sulfate (CaSO₄), there is half a molecule of water.
- Preparation: Formed by heating Gypsum (CaSO₄ · 2H₂O) at 150°C to remove 1.5 molecules of water.
- Reaction with Water: Reacts with water to form Gypsum (CaSO₄ · 2H₂O) again, which causes it to harden.
- Uses:
- In construction for making false ceilings and decorative designs.
- In medical applications for making orthopedic casts.
- In sculpture and mold-making.
- Property: Quick-setting material, but excess water slows down setting.
- Precaution: Absorbs moisture from the air, so it should be stored in airtight containers.
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