What is meant by "water of crystallization" of a substance?

CBSE Class 10 CBSE Class 10 Science
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1

What is meant by “water of crystallization” of a substance ? Describe an activity to show the water of crystallization.

2

Activity to demonstrate water of crystallization :

  1. Take a few crystals of hydrated copper sulphate in a dry test tube and heat the test tube.
  2. We observe water droplets on the walls of the test tube.
  3. The blue colour of copper sulphate crystals is lost and the substance has be-come white. .
  4. Add 2 or 3 drops of water on the sample of copper sulphate obtained after heating.
  5. The blue colour of copper sulphate is restored.
  6. In the above activity copper sulphate crystals which seem to be dry contain the water of crystallization and when these crystals are heated the water present in crystals is evaporated and the salt turns white.
  7. Water of crystallization is the fixed number of water molecules present in one formula unit of a salt.