Question

Identify the compound which do not contains water of crystallization.
1. Gypsum
2. Baking Soda
3. Washing soda
4. Blue vitriol

Answer 1

Correct Answer - Option 2 : Baking Soda

Concept -

The water of crystallisation:

• A fixed number of water molecules in one formula of a unit of salt is referred to as crystallisation water.
• Hydrates are crystal salts that contain water during the crystallisation process.
• The formation of pure crystals from an aqueous solution causes the water to crystallise.
• Contaminants are not present in these crystals.
• Heat has a strong effect on these crystals.
• In simpler words, the quantity of water molecules present in one formula unit of salt is known as the water of crystallisation.
• The water in the crystalline framework of a metal complex or a salt that is not directly linked to the metal cation.

​Explanation-

• CuSO4.5H2O
  • CuSO₄.5H₂O is the chemical formula for blue vitriol, which is copper sulphate pentahydrate.
  • There are 5 moles of water in it.
• Baking soda (NaHCO₃)
  •  Often known as sodium bicarbonate, it does not include any water molecules in its crystal structure.
• Na₂CO₃.H₂O
  • It has the chemical formula for washing soda, which is a sodium carbonate monohydrate.
  • There is one mole of water in it.
• CaSO₄.2H₂O
  • It has the chemical formula for Gypsum, which is a sulphate dihydrate.
  • There are two moles of water in there.
• As Baking soda does not include any water molecules in its crystal structure, it is the correct answer to this question.