Which one of the following statements is NOT correct ?

  1. A. Water of crystallization is the fixed number of water molecules present in one formula unit of a salt
  2. B. The molecular formula of Plaster of Paris is \\( CaSO_{4} \\cdot 2H_{2}O \\)
  3. C. Washing soda is used for removing the permanent hardness of water
  4. D. The atmosphere of Venus is made up of thick white and yellow clouds of sulphuric acid

Correct Answer: B. The molecular formula of Plaster of Paris is \\( CaSO_{4} \\cdot 2H_{2}O \\)

Explanation

The formula for Plaster of Paris is calcium sulphate hemihydrate, \\( CaSO_{4} \\cdot \\frac{1}{2}H_{2}O \\), not \\( CaSO_{4} \\cdot 2H_{2}O \\) (which is gypsum).

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