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The number of water molecules in gypsum, dead burnt plaster and plaster of paris, respectively are:

1. 2, 0 and 1
2. 0.5, 0 and 2
3. 5, 0 and 0.5
4. 2, 0 and 0.5

Correct answer: 2, 0 and 0.5

Solution

Gypsum contains two water molecules in its chemical structure, while dead burnt plaster has no water molecules as it is an anhydrous form. Plaster of Paris, which is a partially dehydrated form of gypsum, contains half a water molecule in its formula.

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