Question

Why does the color of copper sulphate change when an iron nail is dipped in it ?

Answer 1

When an iron nail is dipped in copper sulphate solution, it becomes brownish in colour because iron has replaced copper from its solution. This is because iron is more reactive than copper.

Thus, the amount of copper sulphate decreases and its colour fades.

Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

This is a displacement reaction.