M i = the molar mass of each gas
The molar mass of dry air with oxygen, nitrogen and the other components as indicated below is 28.9647 g/mol. Composition and content of each gas in air is given in the figures and the table below.
See also Air Density at varying pressure, Density and specific weight at varying temperature , Diffusion Coefficients for Gases in Air , Dynamic (absolute) and kinematic viscosity , Prandtl Number , Specific heat at varying temperature and Specific heat at varying pressure , Thermal Conductivity , Thermal Diffusivity , Properties at gas-liquid equilibrium conditions and Air properties , for other properties of air.
For full table with Molar mass an Molar mass in Air - rotate the screen!
|Components in dry air|| Volume ratio = Molar ratio, |
compared to dry air
| Molar Mass ||Molar mass in air|
|Name||Formula||[mol/mol air ]||[vol %]|| [g/mol] |
| [g/mol air ] |
[kg/kmol air ]
|Carbon dioxide||CO 2||0.00033||0.033||44.010||0.014677||0.051|
|Average molar mass of air||28.9647|
The density of dry air can be calculated with the Ideal Gas Law
ρ = P / (R T) (1)
P = pressure (Pa)
R air = 287.05 = individual gas constant [J/kg K]
T = absolute temperature [K]
Example: The density of dry air at atmospheric pressure 101.325 kPa (101325 Pa) and 0 o C (= 273.15 K) can be calculated as
ρ = 101325 [Pa] / (287.05 [J/kg K]*273.15 [K])
= 1.292 [kg/m 3 ]
Water vapor is almost always present in air. The content may vary and the maximum amount possible of water vapor in dry air depends on the temperature of the air.
Water vapor - H 2 O - is composed of one oxygen atom and two hydrogen atoms. Hydrogen is the lightest element with a molar mass of 1 g/mol, while oxygen has 16 g/mol . Thus, the water vapor atom has an molar mass of 18 g/mol, and water vapor is lighter than O 2 with 32 g/mol and N 2 with 28 g/mol .
The vapor in air may saturate to droplets when temperature is decreased or pressure is increased.
Humid air containing water molecules as liquid - droplets - may be more dense than dry air or humid air containing water only as vapor.
Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
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Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.
Dry air is a mechanical mixture of nitrogen, oxygen, argon and several other gases in minor amounts.
Air density at pressure ranging 1 to 10 000 bara (14.5 - 145000 psi) and constant selected temperatures.
Online calculator, figures and tables showing density, specific weight and thermal expansion coefficients of air at temperatures ranging -100 to 1600 °C (-140 to 2900 °F) at atmospheric and higher pressure - Imperial and SI Units.
Diffusion coefficients (D12) for gases in large excess of air at temperatures ranging 0 - 400 °C.
Online calculator, figures and tables with dynamic (absolute) and kinematic viscosity for air at temperatures ranging -100 to 1600°C (-150 to 2900°F) and at pressures ranging 1 to 10 000 bara (14.5 - 145000 psia) - SI and Imperial Units.
Prandtl number for air vs. temperature and pressure.
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Specific Heat Ratio of air at temperatures ranging -40 - 1000 degC (-40 - 1500 degF) at standard atmospheric pressure - Imperial and SI Units.
Figures and tables with isobaric (Cp) and isochoric (Cv) specific heat of air at constant temperature and pressure ranging 0.01 to 10000 bara.
Online calculator with figures and tables showing specific heat (Cp and Cv) of dry air vs. temperature and pressure. SI and imperial units.
Speed of sound in air at standard atmospheric pressure with temperatures ranging -40 to 1000 °C (-40 to 1500 °F) - Imperial and SI Units.
Online calculator with figures and tables showing air thermal conductivity vs. temperature and pressure. SI and imperial units.
Figures and tables withdry air thermal diffusivity vs. temperarure and pressure. SI and Imperial units.
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Thermodynamic properties of dry air - specific heat, ratio of specific heats, dynamic viscosity, thermal conductivity, Prandtl number, density and kinematic viscosity at temperatures ranging 175 - 1900 K.
Density and specific volume of dry air and water vapor at temperatures ranging 225 to 900 degF (107 to 482 degC).
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The mole is the SI base unit for an amount of a substance.
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Chemical, Physical and Thermal Properties of Nitrogen - N2.
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Chemical, Physical and Thermal Properties of Oxygen - O2.
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The Universal and Individual Gas Constants in fluid mechanics and thermodynamics. Individual gas constants for the most common gases.
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