Dear student. Magnesium is more reactive than hydrogen and it displaces hydrogen from dilute acids. Magnesium reacts with dilute sulphuric acid to form magnesium sulphate and hydrogen gas is evolved. So, when a magnesium ribbon is reacted with dilute sulphuric acid, the reaction is shown below - Mg(s)+H2SO4(aq) →MgSO4(aq)+H2(g). Regards