Multiple choice

The formula of plaster of paris is ______.

  1. CaSO4

  2. CaSO4.2H2O

  3. 2CaSO4.4H2O

  4. 2CaSO4.H2O

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Plaster of Paris is calcium sulfate hemihydrate with formula 2CaSO4·H2O or CaSO4·0.5H2O. When mixed with water, it rehydrates to form gypsum (CaSO4·2H2O) and hardens. The hemihydrate form is what makes it useful for casts and molds.

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