An iron nail is dipped in the solution of copper sulphate for about 30 minutes, state the change in colour observed. Give the reason for the change.

When an iron nail is dipped in a blue copper sulphate solution for about 30 minutes, the following changes are observed:

1. Change in Solution Color: The blue color of the copper sulphate solution gradually fades and turns light green.
2. Change on the Iron Nail: A reddish-brown coating of copper metal is deposited on the surface of the iron nail.

Reason for the change:

This is a single displacement reaction. Iron ($\text{Fe}$) is more reactive than copper ($\text{Cu}$) according to the reactivity series. Therefore, iron displaces copper from its salt solution ($\text{CuSO}_4$) to form iron(II) sulphate ($\text{FeSO}_4$), which is light green in color, while metallic copper is set free and deposits on the nail.

The balanced chemical equation is:

$$\text{Fe(s)} + \text{CuSO}_4\text{(aq) [blue]} \rightarrow \text{FeSO}_4\text{(aq) [light green]} + \text{Cu(s) [reddish-brown]}$$