Other uses of the Ideal Gas Law

PV = nRT

Molar Volume:
It is convenient to recognize in some calculations that because the same volume of different gases at the same P and T contains the same number of particles, one mole of most common gases occupies 22.4

at 0°C and atmospheric pressure.

When it is used in combination with other familiar relationships, the ideal gas law enables calculation of gas densities, concentrations and molar mass.

Concentration:

c(gas) =	n	=	P
	V		RT

See at the right how the concentration of a gas in mol m^–3 can be calculated from its partial pressure at a given temperature.

Density:

d(gas) =	m	=
	V

n(M)	=	P(M)
V	=	RT

Because the concentration of a pure gas in mol m^–3

(

)

and its density in

g m^–3

) are related through the molar mass of the gas, the ideal gas equation can also be used

to calculate molar mass from density
density from mass and molar mass.

Molar mass:

PV =	(	m	)	RT
		M

The modified version of the Ideal Gas Law given at the right shows how the molar mass of a gas can be calculated from knowledge of the mass of gas, the volume it occupies and the temperat ure.