what is meant by water crystallization?how would you show the blue copper sulphate crystals contain water of crystallization?

Water of crystallisation is the number of water molecules that combine chemically in definite molecular proportion, with the concerned salt in the crystalline state. This water is responsible for the geometric shape and colour of the crystals.

For example: the CuSO4.5H2O

Copper sulphate crystals are blue in colour. However, when copper sulphate is heated in a china dish for some time, the blue colour disappears and it becomes white-gray in colour. This is the anhydrous copper sulphate. The reaction is written as follows


Thus the blue colour of copper sulphate crystals is due to water of crystallisation, which are lost when it is heated. Hence the blue colour of solution disappears. This proves that copper sulphate contains water of crystallisation.

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Ans:  Some salts crystallise out from their saturated aqueous solution with a definite number of molecules of water called water of crystallisation. Such salts are called hydrated salt .on heating, the hydrated salt loose water of crystallisation and lose their colour , if coloured then it become white.

we show it by chemical reaction:

when, CuSO4.5H2O   HEAT     CuSO4  + 5H2O

 Hydrated copper sulphate (blue)  HEAT      ANHYDROUS COPPER SULPHATE ( white in colour) +    WATER OF CRYSTALLISATION

  so by reaction , it is seen that blue coloured copper sulphate  upon heating changed into white colour and  water of cryatallisation is removed.

sorry ,if answer is wrong.


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Water of crystillization is is a fixed number of water molecules attached with certain salts in crystilline form.

Eg: CuSO4.5H2O, Na2CO3.10H2O,etc

To show that the blue copper sulphate crystals contain water of crystillization, see the activity of your science textbook, pg:32 activity .

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