The solutions of `ZnSO_4, FeSO_4, CuSo_4 and AgNO_3`, are taken in four different test tubes. Suppose, an iron nall is kept immersed in each one.
a) In which test tube the iron nail under goes a colour change?
b) What is the reaction taking place here?
c) Justify your answer. (Refer reactivity series of metals).

Explanation

a) Iron nall undergoes a colour change occured in the test tube with copper sulphate `(CuSO_4)` solution.
b) `Fe+ CuSO_4 rarr FeSO_4 +Cu`
c) The blue solution changes to yellowish brown, because iron displaces copper from copper sulphate solution, Iron can displaces from its own and silver solution, but there is no observable change in the colour here.