Iron nails are dipped into blue copper sulphate solution. After some time iron nails are:

• dissolved and blue color is discharged

• dissolved but blue color is not discharged

• not dissolved but the blue color is not discharged

• not dissolved but the blue color is discharged

D.

not dissolved but the blue color is discharged

Iron is more reactive than copper, thus displaces copper from copper sulphate solutions.

$\mathrm{Fe} + \underset{\mathrm{Blue}}{{\mathrm{CuSO}}_4} \to \underset{\mathrm{green}}{{\mathrm{FeSO}}_4} + \underset{\mathrm{red}-\mathrm{brown}}{\mathrm{Cu}}$

The copper formed get deposited over the iron nail and blue colour of the solution gradually disappears and removed from the solution.