Under conditions, 22.4 L/mol is accurate, to three sig figs. However, gases in reactions are rarely at 273 K or 1.00 atm. When any non-standard conditions are used, we can get a better approximation of quantities using the law, in conjunction with stoichiometry. There are two kinds of gas stoichiometry problems: a) Use the then do stoichiometry, or b) Do stoichiometry, then use the IGL