Blue copper sulphate became white on heating and turned blue again on adding water. What was proved?
Answer and explanation
Correct answer: Water of crystallisation was related to the colour
The governing concept is water of crystallisation in hydrated salts. Blue copper sulfate crystals are CuSO4·5H2O. Heating removes this crystallisation water and produces white anhydrous CuSO4. Adding water restores the hydrated blue form. Hence the observation proves that the crystal water is associated with the colour, so option A is correct. Copper sulfate is neither sugar nor common salt, and water does not convert copper into gold.
Frequently asked questions
What is the correct answer to this question?
Water of crystallisation was related to the colour
Why is this the correct answer?
The governing concept is water of crystallisation in hydrated salts. Blue copper sulfate crystals are CuSO4·5H2O. Heating removes this crystallisation water and produces white anhydrous CuSO4. Adding water restores the hydrated blue form. Hence the observation proves that the crystal water is associated with the colour, so option A is correct. Copper sulfate is neither sugar nor common salt, and water does not convert copper into gold.
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.
