Why does white anhydrous copper sulphate become blue again when water is added?
Answer and explanation
Correct answer: It becomes hydrated copper sulphate
The governing concept is hydration and water of crystallisation. Heating removes water from blue CuSO₄·5H₂O and forms white anhydrous CuSO₄. When water is added again, the salt incorporates the water molecules and the hydrated crystal form is restored, giving the characteristic blue colour. Therefore option A is correct; the other options describe unrelated substances or products.
Frequently asked questions
What is the correct answer to this question?
It becomes hydrated copper sulphate
Why is this the correct answer?
The governing concept is hydration and water of crystallisation. Heating removes water from blue CuSO₄·5H₂O and forms white anhydrous CuSO₄. When water is added again, the salt incorporates the water molecules and the hydrated crystal form is restored, giving the characteristic blue colour. Therefore option A is correct; the other options describe unrelated substances or products.
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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