composition of air

 
 

Air is a mixture of gases, approx. 78% nitrogen and 21% oxygen, with small amount of water vapor (humidity), argon, and carbon dioxide, and traces of neon, methane, and various other components; it is usually modeled as a uniform (no variations or fluctuations) gas with properties that are averaged from all the individual components. The composition of air is unchanged until the height of approx. 10 km.

 

gas dry air composition molar mass boiling point
vol % mass % g / mol oC

nitrogen

 N2
78 .084
75 .47
28 .013
-195 .79

oxygen

 O2
20 .9476
23 .20
31 .999
-182 .95

argon

 Ar
0 .934
1 .28
39 .948
-185 .85

carbon dioxide

 CO2
0 .0314
0 .046
44 .010
-78 .4

neon

 Ne
1 .818 E-3
1 .2 E-3
20 .180
-246 .08

helium

 He
5 .24 E-4
7  E-5
4 .003
-268 .93

methane

 CH4
2   E-4
1 .05 E-4
16 .042
-161 .5

krypton

 Kr
1 .14 E-4
3  E-4
83 .80
-153 .22

hydrogen

 H2
5  E-5
~ 0
2 .016
-252 .87

xenon

 Xe
8 .7 E-6
4  E-5
131 .29
-108 .12

average molar mass
28 .965

 

  dry air composition
 
 

Source: CRC Handbook of Chemistry and Physics (D.R. Lide, Editor-in-Chief), 83rd edition (2002-2003), CRC Press, Boca Raton, FL, 2002, p.14-19.  [NH05]

 
 
UPDATED : 2004-12-23 WEBSITE  EDITOR : Krešimir J. Adamić