## The Ideal Gas Law: Molar Volume of an Ideal Gas

**James Richard Fromm**

The ideal gas law *pV* = *nRT* can be rearranged to *V*/*n* = *RT*/*p*,
and the ratio *V*/*n* is the **molar volume** of any substance, so
the molar volume of an ideal gas is always *RT*/*p*. The SI pressure unit, the
pascal, is also the joule per cubic meter (J/m^{3}), and so the ideal gas law
predicts a molar volume at one bar pressure of 24.789... L/mol for any ideal gas at 25^{o}C
and a molar volume of 22.7106... L/mol at 0^{o}C. At one atmosphere pressure, the
molar volume of an ideal gas would be 24.465 L/mol at 25^{o}C and 22.414 L/mol at
0^{o}C. Most real gases at atmospheric pressure have a molar volume very close to
that predicted by the ideal gas law.

Copyright 1997 James R. Fromm