To calculate the molar mass of a gas, without knowing density, we would alter the equation:
PV = (mass / molar mass)(RT)
we know density and the units are mass / volume
altering the equation to accommodate density
PV= mass x RT x molar mass.....taking note that mass / volume = density, g/L
P = dRT / molar mass
solving for molar mass:
molar mass = dRT/P
3.44g/L x 0.0821L-atm/mole-K x 273K / 1atm = molar mass = 77.1g/mole