Gas
a
b
Pa ∙ m6 ∙ mol-2
10-6 ∙ m3 ∙ mol-1
H2
0.0248
26.6
He
0.00346
23.7
N2
0.141
39.1
O2
0.138
31.8
H2O
0.554
30.5
CH4
0.228
42.8
CO2
0.364
42.7