White anhydrous copper sulphate turns blue when water is added. What does this show?
Answer and explanation
Correct answer: Presence of water
Anhydrous copper sulphate, CuSO₄, is white because it contains no water of crystallisation. When water is added, hydrated copper sulphate, commonly represented as CuSO₄·5H₂O, forms and the solid becomes blue. This characteristic colour change is therefore used as a simple test for water, making option A correct. Chlorine, hydrogen, and nitrogen do not cause this specific white-to-blue change in anhydrous copper sulphate.
Frequently asked questions
What is the correct answer to this question?
Presence of water
Why is this the correct answer?
Anhydrous copper sulphate, CuSO₄, is white because it contains no water of crystallisation. When water is added, hydrated copper sulphate, commonly represented as CuSO₄·5H₂O, forms and the solid becomes blue. This characteristic colour change is therefore used as a simple test for water, making option A correct. Chlorine, hydrogen, and nitrogen do not cause this specific white-to-blue change in anhydrous copper sulphate.
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.
