What happens when an iron nail is immersed in copper sulphate solution for some time? Justify your observation.

A single displacement reaction takes place, when an iron nail is placed in copper sulfate solution. The chemical reaction can be written as:

Fe (s) + CuSO4 (aq) -> FeSO4 (aq) + Cu (s)

In this case, iron, being more reactive than copper, will displace it from the solution. That is, ferrous ions or Fe(II) will go into the solution, while curic or Cu(II) will be deposited onto the nail. This cause the solution color to change from blue to green. The copper coating on the nail will give it a refdish-brown color. And we end up with solid copper and a solution of ferrous sulfate.

In general, more reactive species displaces less reactive species from a solution, as shown here by displacement of copper by iron.

Hope this helps.