Question

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Answer 1

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> When an iron nail dipped in the copper sulphate solution, iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore the colour of the copper sulphate solution changes. The reaction is:
$Fe+CuS{O}_4\to FeS{O}_4+Cu$