Question

why does the colour of copper sulphate solution change when on iron nail is dippedin it

Answer 1

this reaction takes place which leads to displacement of Cu from it's sulphate solution

Answer 2

Fe being more reactive than Cu, displaces Cu frm CuSO4 solution.

Therefore the solution turns its blue colour n turns green in colour as FeSO4 crystals r green in colour.

reaction

CuSO4 +Fe --> FeSO4 +Cu
(blue). (green). (black)

hope it helps!
n plz follow if u lyk my answer