Question

Add nail in CuSO4 solution. The colour of CuSO4 disappears why??

Answer 1

bcause iron displaces copper from its salt solution

Answer 2

This is because of the formation of Ferrous Sulphate.The blue colour fades and turns into light green)
Fe+CuSO4(aq)=FeSo4+Cu
It is a displacement reaction.
Hope it helps:)