Question

Why does the iron nail become brownish in colour and the blue colour of copper sulphate solution fade?

Answer 1

When an iron nail dipped in the copper sulphate solution than iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore the colour of the copper sulphate solution changes.
The reaction involved is 
  Fe + CuSO4 ------FeSO4+Cu

Answer 2

Answer:

The iron nail become brownish in colour and the blue colour of copper sulphate solution fade because when an iron nail dipped in the copper sulphate solution then iron displaces copper from the copper sulphate because iron is more reactive than copper therefore the colour of copper sulphate solution changes.

Reaction involved in it is

Fe+cuso4->feso4+cu

I hope it is helpful......