This activity demonstrates the concept of water of crystallization present in salt
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Activity 2.15 Water of Crystallization in Copper Sulphate
Aim of the activity
To observe the change in colour of copper sulphate when heated.
Materials Required
1. Copper sulphate crystals
2. Dry boiling tube
3. Test tube
4. Burner
5. Dropper
6. Water
Procedure
We take a few crystals of copper sulphate in a dry boiling tube and hold it with holder
and heat over a flame.
We observe the changes in colour of salt.
After heatig, we keep the tube to cool and observe any water droplets inside the tube.
Now we add 2-3 drops of water and observe the change in the colour of salt.
.png "Activity 2.15 Class 10 Science Heating of Copper Sulphate Crystals")
Observation
We observe
1. The blue crystals of copper sulphate turn into white powder on heating.
2. Water droplets appear on the inner side of boiling tube.
3. The blue colour is restored on adding water to the salt.
Explanation
Copper sulphate crystals contain five molecules of water of crystallization.
On heating, these water moleucles are removed and anhydrous copper sulphate is formed which is whtite in colour.
CuSO4.5H2O → CuSO4 + 5H2O
When water is added to the anhydrous copper sulphate, the blue colour is restored.
CuSO4 + 5H2O → CuSO4.5H2O
Conclusion
We can conclude that copper sulphate crystals contain water of crystallization which gives it blue colour. So, water of crystallization gives particular colour to the salt.
Frequently Asked Questions
1. Why does copper sulphate lose its colour on heating?
Answer –
Because copper sulphate loses water of crystallization and anhydrous copper
sulphate is formed which is white in colour.
2. What is water of crystallization?
Answer -The fixed number of water molecules chemically bonded in crystals of salts.
3. What is the formula of copper sulphate?
Answer –
CuSO4.5H2O
All Activities Acids , Bases and Salts
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