(4) The reaction that occurs ondipping an iron nail in coppersulphate solution is as follows: Fe+CuSO4→FeSO4+Cu As iron is more reactive than copperthus it will displace the copper fromthe copper sulphate solution andform iron sulphate giving thesolution a faded appearance. Thecopper metal gets deposited overthe iron nail giving it a brownishcolour. Hence, it is an example ofdisplacement reaction. Here, iron(Fe) is oxidised while copper (Cu) isreduced hence it is an example ofredox reaction also.