Say you have equimolar quantities of [[hydrogen]] (H<sub>2</sub>) and [[oxygen]] (O<sub>2</sub>). Since 2 [[mole]]s of hydrogen are required for every 1 mole of oxygen, when all the hydrogen is used up there is still leftover oxygen. Thus, hydrogen is the limiting reactant, because it is used up first. | Say you have equimolar quantities of [[hydrogen]] (H<sub>2</sub>) and [[oxygen]] (O<sub>2</sub>). Since 2 [[mole]]s of hydrogen are required for every 1 mole of oxygen, when all the hydrogen is used up there is still leftover oxygen. Thus, hydrogen is the limiting reactant, because it is used up first. |