What causes the blue colour of copper sulphate crystals?
Answer and explanation
Correct answer: Water of crystallisation
The governing concept is water of crystallisation in hydrated salts. Blue copper sulphate crystals are represented as CuSO4·5H2O, meaning that a fixed number of water molecules are incorporated into the crystal structure. This hydrated form has its characteristic blue colour. On heating, the water is removed and anhydrous copper sulphate becomes white. Hence option A is correct; sodium ions, chlorine gas and carbon dioxide are not responsible for this colour.
Frequently asked questions
What is the correct answer to this question?
Water of crystallisation
Why is this the correct answer?
The governing concept is water of crystallisation in hydrated salts. Blue copper sulphate crystals are represented as CuSO4·5H2O, meaning that a fixed number of water molecules are incorporated into the crystal structure. This hydrated form has its characteristic blue colour. On heating, the water is removed and anhydrous copper sulphate becomes white. Hence option A is correct; sodium ions, chlorine gas and carbon dioxide are not responsible for this colour.
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.
