Question

Why does the blue colour of copper sulphate soln starts fading when zinc rod is dipped in it?

Answer 1

Zinc is more reactive than copper. Hence it easily displaces copper from it's sulphate solution.So the blue color starts fading and copper gets deposited on the rod.

Answer 2

The CuSO4 liquid is of blue color while the ZnSO4 solution is transparent.

Zn(s) + CuSO4(aq) -> Cu(s) + ZnSO4 (aq).

When zinc and copper sulfate react in the aqueous phase, an uncomplicated displacement effect will take form in which the zinc will dismiss the copper from the copper sulfate to produce zinc sulfate so the blue gradually fades.