Air Composition

Dry air is a mechanical mixture of nitrogen, oxygen, carbon dioxide and more

Air is a mixture of gases, 78% nitrogen and 21% oxygen with traces of water vapor, carbon dioxide, argon, and various other components. We usually model air as a uniform (no variation or fluctuation) gas with properties that are averaged from all the individual components.

Gas	Ratio compared to Dry Air (%)		Molecular Mass - M - (kg/kmol)	Chemical Symbol	Boiling Point
	By volume	By weight			K	(oC)
Oxygen	20.95	23.20	32.00	O2	90.2	-182.95
Nitrogen	78.09	75.47	28.02	N2	77.4	-195.79
Carbon Dioxide	0.03	0.046	44.01	CO2	194.7	-78.5
Hydrogen	0.00005	~ 0	2.02	H2	20.3	-252.87
Argon	0.933	1.28	39.94	Ar	84.2	-186
Neon	0.0018	0.0012	20.18	Ne	27.2	-246
Helium	0.0005	0.00007	4.00	He	4.2	-269
Krypton	0.0001	0.0003	83.8	Kr	119.8	-153.4
Xenon	9 10-6	0.00004	131.29	Xe	165.1	-108.1

The water or vapor content in air varies. The maximum moisture carrying capacity of air depends primarily on the temperature.

The composition of air is unchanged until the height of approximately 10.000 m.

The average air temperature diminishes at the rate of about 0.6^oC for each 100 m vertical height

"One Standard Atmosphere" is defined as the pressure equivalent to that exerted by a 760 mm column of mercury at 0^oC sea level and at standard gravity (32.174 ft/sec²).

Common Pressure Units frequently used as alternative to "one Atmosphere"

• 76 Centimeters (760 mm) of Mercury
• 29.921 Inches of Mercury
• 10.332 Meters of Water
• 406.78 Inches of Water
• 33.899 Feet of Water
• 14.696 Pound-Force per Square Inch
• 2116.2 Pounds-Force per Square Foot
• 1.033 Kilograms-Force per Square Centimeter
• 101.33 Kilopascal

More about Temperature, Density, Specific heat, Thermal Conductivity - the properties of air.

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Related Documents

• Air Properties Air properties - temperature, density, specific heat, thermal conductivity, expansion coefficient, kinematic viscosity and Prandtl number for temperatures between -150^oC and 400^oC.
• Specific Heat Ratio of Air Specific Heat Ratio of air at temperatures from -40 to 1.000^oC (-40 to 1.500^oF) at standard atmospheric pressure - in Imperial and SI Units
• Humid Air and the Ideal Gas Law The Ideal Gas Law relating pressure, temperature, and volume of an ideal or perfect gas can also be used for air with water vapor - moist air
• Molecular Mass of Air Dry air is a mixture of gases where the molecular weight can be calculated by adding the weight of each component
• Density of Dry Air, Water Vapor and Moist Humid Air Calculating the density of dry air, water vapor or the mixture of air and water vapor - moist or humid air
• Dry Air Properties Dry air properties at temperatures ranging 175 - 1900 K - specific heat capacity, ratio of specific heats, dynamic viscosity, thermal conductivity, Prandtl number, density and kinematic viscosity
• Nitrogen - Specific Heat Capacity Specific heat capacity of Nitrogen Gas - N2 - at temperatures ranging 175 - 6000 K
• Oxygen - Specific Heat Capacity Specific heat capacity of Oxygen Gas - O2 - at temperatures ranging 175 - 6000 K
• Ideal Gas Properties Oxygen Enthalpy, Internal Energy and Entropy of Oxygen