Question

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

NCERT Class 10th Science Chapter 1 Chemical Reactions and Equations

Answer 1

fe is more reactive than copper therefore it displaces copper in the solution of copper sulphate and red brown substance deposit on iron nail which is copper. the reaction is displacement reaction
   CuSO4  +  Fe  ⇒   FeSO4 + Cu
  (copper sulphate)     (ferrous sulphate)

Answer 2

iron is more reactive than copper..it displace copper from copper sulphate sol.acc to following reaction.....
fe+ cuso4---->feso4+cu
thus as copper sulphate react to form iron 2 sulphate ,the blue colour of copper sulphate fades