A reaction system in equilibrium according to reaction.
2SO2(g)+O2(g)⇌2SO3(g) in one litre vessel at a given temperature was found to be 0.12 mole each of SO2 and SO3 and 5 mole of O2. In another vessel of one litre contains 32 g of SO2 at the same temperature. What mass of O2 must be added to this vessel in order that at equilibrium 20% of SO2 is oxidized to SO3?