A hot air balloon has a $\pu{500 m^3}$ volume. How much mass of normal air fits into the balloon, if the relative molar mass is $\pu{28.8 g/mol}$?
I am not sure if I should simply use the $PV=nRT$ formula and therefore
$$1\times500= m/28.8 \times 273 \times 8.31 .$$
I feel that there is something wrong, can anyone enlighten me with the right formula or the basic concept of solving this kind of questions?