GEK Wiki / Properties of Air
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# Properties of Air

last edited by 11 years, 7 months ago

### Components in Dry Air

The two most dominant components in dry air are Oxygen and Nitrogen. Oxygen has a 16 atomic unit mass and Nitrogen has a 14 atomic units mass. Since both of these elements are diatomic in air - O2 and N2, the molecular mass of Oxygen is 32 and the molecular mass of Nitrogen is 28.

Air is a mixture of gases and the total mass can be estimated by adding the weight of all major components as shown here:

 Components in Dry Air Volume Ratio in Dry Air Mass Ratio in Dry Air Molecular Mass - M (kg/kmol) Molecular Mass in Air Oxygen 0.2095 .2320 32.00 6.704 Nitrogen 0.7809 .7547 28.02 21.88 Carbon Dioxide 0.0003 .00046 44.01 0.013 Hydrogen 0.0000005 2.02 0 Argon 0.00933 .0128 39.94 0.373 Neon 0.000018 20.18 0 Helium 0.000005 4.00 0 Krypton 0.000001 83.8 0 Xenon 9E-6 131.29 0 Total Molecular Mass of Air 28.97

(from engineeringtoolbox http://www.engineeringtoolbox.com/molecular-mass-air-d_679.html)

The "Mass Ratio" is useful for combustion calculations (e.g. to get 1kg of oxygen, we need 1/0.2320 = 4.31kg of air).

Air Property Calculator

Under standard conditions (25oC, 1atm), the density of air is about 1.168kgm-3.

Hence 1kg of air would have a volume of:

1kg/1.168kgm-3

= 0.8562m3