Question

peices of blue vitrol were heated in a test tube. on cooling water was added to it. what is reaction

Answer 1

Upon heating, water will escape from blue vitriol.
CuSO4.5H2O --> CuSO4 + 5H2O
On adding water, it will regain its water of crystallisation.
CuSO4 + 5H2O --> CuSO4.5H2O

Answer 2

When pieces of blue vitriol were heated in a test tube, the crystalline structure of blue vitriol broke down to form colourless powder and water evaporates. On cooling when water was added to colourless powder, blue vitriol regains it's blue colour. All the above changes are physical changes

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