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Gas composition

Gas composition: any gas can be characterised by listing the pure substances it contains, and stating for each substance its proportion of the gas mixture's molecule count.

To give a familiar example, air has a composition available here, from CRC Handbook of Chemistry and Physics, 1997 Edition of:

Pure Gas Name Symbol Mole Fraction
Nitrogen N2 0.78084
Oxygen O2 0.209476
Argon Ar 0.00934
Carbon Dioxide CO2 0.000314
Neon Ne 0.00001818
Methane CH4 0.000002
Helium He 0.00000524
Krypton Kr 0.00000114
Hydrogen H2 0.0000005
Xenon Xe 0.000000087

The molar fractions of a complete gas composition must add up to 1.0000.

Note: a gas composition is sometimes also represented in mole percentages. These are simply a factor of 100 larger than molar fractions.

See also

Standard Dry Air -- an agreed upon gas composition for air, the most important point of which to note is that its mixture molar mass is 28.9625. You can contribute to this article by specifying what standards body defines standard dry air, and the name of the standard.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Gas_composition". A list of authors is available in Wikipedia.
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