Question

Why does the blue colour of copper sulphate solution changes to green colour when an iron nail is dipped in it ? Write chemical equation.

Answer 1

The blue colour of the copper sulphate solution changes to green colour because copper of copper sulphate is replaced by iron and forms ferrous sulphate which is green coloured.

This happens because the displacement reaction takes place as iron is a more active metal than copper and hence can replace it.

Fe(s) + $CuS{O}_4\left(aq\right)$ $\to$ $FeS{O}_4\left(aq\right)$ + Cu(s)