Density is a value for
mass, such as kg, divided by a value for volume, such as m3. Density is a
physical property of a substance that represents the mass of that substance per
unit volume. For gases we use the ideal gas equation to solve for density. We do as follows:
PV = nRT
PV = mRT / MM
Density = m/V = PMM / RT
From the conditions given of the O2 system we can determine P/RT as follows:
P/RT = density / MM = 1.30 / 32
P/RT = 0.0406
density of propane = 0.0406 x 44.11 = 1.79 g/L