When given the mass of one reactant or product, we can find the number of moles of a particular product or reactant When given the mass of one reactant or product, we can find the number of moles of a particular product or reactant And vice versa, when given the moles of one product or reactant, we can find the mass of a particular product or reactant And vice versa, when given the moles of one product or reactant, we can find the mass of a particular product or reactant