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Which one of the following statements is NOT correct?

Options

  1. AWater of crystallization is the fixed number of water molecules present in one formula unit of a salt
  2. BThe molecular formula of Plaster of Paris is CaSO₄ 2H₂O
  3. CWashing soda is used for removing the permanent hardness of water
  4. DThe 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 CaSO₄ 2H₂O

Step-by-step solution

Water of crystallization is the fixed number of water molecules present in one formula unit of a salt. This statement is correct. The chemical formula of Plaster of Paris is CaSO₄ 1 2 H₂O (calcium sulphate hemihydrate). The formula CaSO₄ 2H₂O represents gypsum. Thus, this statement is incorrect. Washing soda ( Na₂CO₃ 10H₂O ) is used for removing the permanent hardness of water by precipitating calcium and magnesium ions as insoluble carbonates. This statement is correct. The atmosphere of Venus is made up of thick

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