O Thus, 1.0 g Mg reactis with 0.67 . g O But only 0.56g O is available which less than 0.67 g is. Thus, O . is the limiting reagent. MOLE & EQUIVALENT CONCEPT Further, 16g O reacts with 24g of Mg. 0.56g O will react with 0.56 0.84 Mg g x Amount of Mg left unreacted = 1.0 – 0.84g = 0.16g Mg, Hence, Mg is present in excess and 0.16 g Mg is left behind unreacted.