White anhydrous copper sulphate turns blue when water drops are added. What does this prove?
Answer and explanation
Correct answer: Water restores the colour by forming hydrated copper sulphate
The governing concept is water of crystallisation. Anhydrous copper sulphate, CuSO4, is white because this water has been removed. When water is added, hydrated copper sulphate, CuSO4·5H2O, forms and the characteristic blue colour returns. Therefore option A correctly links the observed colour change with the presence of water; the other options do not describe this reversible hydration.
Frequently asked questions
What is the correct answer to this question?
Water restores the colour by forming hydrated copper sulphate
Why is this the correct answer?
The governing concept is water of crystallisation. Anhydrous copper sulphate, CuSO4, is white because this water has been removed. When water is added, hydrated copper sulphate, CuSO4·5H2O, forms and the characteristic blue colour returns. Therefore option A correctly links the observed colour change with the presence of water; the other options do not describe this reversible hydration.
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.
