Question

Why does the colour of copper sulphate solution change when an iron nail is kept immersed in it?

Answer 1

The colour of copper sulphate solution changes when an iron nail is kept immersed in it because a displacement reaction occurs between copper sulphate and iron to produce ferrous sulphate solution, which is green in colour.

\[\ce{\underset{(Blue solution)}{\underset{Copper sulphate}{CuSO4_{(aq)}}} + \underset{(Nail)}{\underset{Iron}{Fe_{(s)}}} -> \underset{(Greenish solution)}{\underset{Ferrous sulphate}{FeSO4_{(aq)}}} \underset{(Reddish brown nail)}{\underset{Copper}{Cu_{(s)}}}}\]