(a) When dilute sulphuric acid is poured on a copper plate, there will be evolution of hydrogen gas along with the formation of blue color crystals of copper sulphate.
CuSO4 + H2SO4 → CuSO4 + H2
(b) Iron being more reactive displaces copper from copper sulphate solution. In this reaction, the blue colour of copper sulphate fades and there is deposition of copper on the iron nails.
Fe + CuSO4 → FeSO4 + Cu