With all of the information given (pressure, volume, temperature, and the molar mass), we need a formula that relates this all together. The formula we need is the ideal gas law, PV=nRT. Since the pressure is defined in millimeters of mercury, we need the R value that correlates with this, which is 62.4; on top of this, we need the temperature in Kelvin - simply add 273.15 to convert from Celsius. With all of this information, simply plug-and-chug:
PV=nRT (800)(3.7) = n(62.4)(37 + 273.15) n = 0.1529 moles
Finally, the problem is asking the amount of air in grams. We have moles, so all we need to do is multiply that value by the molar mass.
0.1529 moles x 29 grams per mole = 4.435 grams of air
The molecular formula is a whole number multiple of the empirical formula. that is, if the mole wt is 219.9 gms/mole and the empirical formula weight is 110 gms/mole*, then the whole number multiple is 219.9/110 = 2 => Molecular formula => (P₂O₄)₂ => P₄O₆.
