Why do blue copper sulphate crystals become white on heating?
Answer and explanation
Correct answer: Water of crystallisation is removed
The governing concept is water of crystallisation: some salts contain a fixed number of water molecules within their crystal structure. Blue copper sulphate is CuSO₄·5H₂O. On heating, these water molecules are driven off, producing anhydrous CuSO₄, which is white. Thus option A is correct. The copper does not become a gas, sulphate does not turn into water, and oxygen is not added.
Frequently asked questions
What is the correct answer to this question?
Water of crystallisation is removed
Why is this the correct answer?
The governing concept is water of crystallisation: some salts contain a fixed number of water molecules within their crystal structure. Blue copper sulphate is CuSO₄·5H₂O. On heating, these water molecules are driven off, producing anhydrous CuSO₄, which is white. Thus option A is correct. The copper does not become a gas, sulphate does not turn into water, and oxygen is not added.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
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