Gas Constant R

Gas Constant - R

The Individual Gas Constant depends on the particular gas and is related to the molecular weight of the gas. The value is independent of temperature.

In the imperial system the units for the individual gas constant are ft lb/slug ^oR. In the SI system the units are J/kg K.

The Individual Gas Constant for some gases:

Gas	Individual Gas Constant - R
	Imperial Units (ft lb/slug oR)	SI Units (J/kg K)	Molecular Weight (g/mole)
Argon, Ar		208	39.94
Acetylene		319	26
Ammonia		488	17
Carbon Dioxide, CO2	1130	188.9	44.01
Carbon Monoxide, CO		297	28.01
Carbonic acid		189	44
Helium, He	12420	2077	4.003
Hydrogen, H2	24660	4124	2.016
Methane - natural gas, CH4	3099	518.3	16.04
Nitrogen, N2	1775	296.8	28.02
Oxygen, O2	1554	259.8	32
Propane, C3H8		189	44.09
Sulfur dioxide, SO2 (sulfuric acid)		130	64.07
Air	1716	286.9	28.97
Water vapor	2760	461.5	18.02

• More material properties

The Universal Gas Constant - R_u

The Universal Gas Constant - R_u - appears in the ideal gas law and can be expressed as the product between the Individual Gas Constant - R - for the particular gas - and the Molecular Weight - M_gas - for the gas, and is the same for all ideal or perfect gases:

R_u = M_gas R         (1)

where

R_u = universal gas constant

M_gas = molecular weight of the ideal gas or mixture of gases

The Molar Weight of a Gas

The molar weight of a gas can be calculated like

1 / M_gas = (f₁ / M₁ + .... + f_n / M_n)         (2)

where

f = mass of the gas relative to the total mass of the mixture

M = molecular weight of the gas

The Universal Gas Constant - R_u - in alternative Units

• atm.cm³/(mol.K) : 82.0575
• atm.ft³/(lbmol.K) : 1.31443
• atm.ft³/(lbmol.^oR) : 0.73024
• atm.l/(mol.K) : 0.08206
• bar.cm³/(mol.K) : 83.14472
• bar.l/(mol.K) : 0.08314472
• Btu/(lbmol.^oR) : 1.9859
• cal/(mol.K) : 1.9859
• erg/(mol.K) : 83144720
• hp.h/(lbmol.^oR) : 0.0007805
• inHg.ft³/(lbmol.^oR) :  21.85
• J/(mol.K) :  8.3144598 
• kJ/(kmol.K) :  8.3144598
• J/(kmol.K) : 8314.472
• (kgf/cm²).l/(mol.K) : 0.084784
• kPa.cm³/(mol.K) : 8314.472
• kWh/(lbmol.^oR) : 0.000582
• lbf.ft/(lbmol.^oR) : 1545.349
• mmHg.ft³/(lbmol.K) : 999
• mmHg.ft³/(lbmol.^oR) : 555
• mmHg.l/(mol.K) : 62.364
• Pa.m³/(mol.K) : 8.314472
• psf.ft³/(lbmol.^oR) : 1545.349
• psi.ft³/(lbmol.^oR) : 10.73
• Torr.cm³/(mol.K) : 62364