The most common oxosalt of copper (II) is blue virtiol. It has the composition

Options

A. `CuSO_(4) . 4H_(2)O`
B. `CuSO_(4) . 5H_(2)O`
C. `CuSO_(4) . 3H_(2)O`
D. `CuSO_(4) . H_(2)O`

Answer

B

Explanation

It is made commercially by spraying hot dilute sulphuric acid on scrap copper in the presence of a current of air, when the metal slowly dissolves:
`2Cu + 2H_(2)SO_(4) + O_(2) rarr 2CUSO_(4) + 2H_(2)O`
The crude copper (II) sulphate obtains iron (II) sulphate as impurity. Dilute nitric acid is added to oxidise iron (II) to iron (III) sulphate, which remains in solution after srystallization. The pentahydrate, `CuSO_(4)` . `5H_(2)O` crystallizes out. In the laboratory it is prepared by dissolving copper oxide in dilute sulphuric acid and concentrating the solution, when deep blue crystals of the pentahydrate, known as blue virtiol, are obtained:
`CuO + H_(2) SO_(4) rarr CuSO_(4) + H_(2)O`
Crystalline copper sulphate is readily soluble in water. The salt, `CuSO_(4)` . `5H_(2)O`, is insoluble in a alchol and is precipitated on adding alcohol to the aqueous solution.