Question

few CuSO4 crystals are heated in a boiling tube
A.) what is the colour before heating and after heating
B.) reason for the colour change
C.) can its original colour be restored? how?

Answer 1

1. The colour of CuSO4 is blue but after the heating it turns colourless.

2. because water of Crystallization is lost on heating.

3. its original colour be restored by adding water in CuSO4.

Answer 2

1. Before heating it was blue but after, it turned colorless (white).  
2. This is because, CuSO4 crystals have water as part of their structure. OR, their actual formula is CuSO4.5H2O.When the blue crystals are heated the water of crystallization is lost and what remains is anhydrous copper sulphate (CuSO4).  
3. As this is a reversible reaction, it's colour can be restored by adding water to it