The changes observe when pieces of blue vitriol were heated in a test tube and on cooling, water was added to it are:
i. On heating, the crystalline structure of blue vitriol broke down to form a colorless powder.
ii. On adding water, the color changes back to blue color.
Explanation: When blue vitriol (hydrated CuSO4) is heated, it becomes anhydrous and colorless (white).
CuSO4.5H2O → CuSO4 + 5H2O
Now, when water was added, it regained its blue colour and becomes hydrated again.
CuSO4 + H2O → CuSO4.5H2O
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