Stoichiometry is the quantitative relationship between reactants and products. It tells us how much of "A" must react with how much of "B" to produce how much of "C". We have considered the molecular view (atoms & molecules) of the chemical equation, now we will consider an extension of this view that corresponds to real-life quantities useful in laboratory work. In this macroscopic interpretation, stoichiometric coefficients correspond to mole quantities and the masses are in grams using the molar mass relations.