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/m3), and so the ideal gas law predicts a molar volume at one bar pressure of 24.789... L/mol for any ideal gas at 25oC and a molar volume of 22.7106... L/mol at 0oC. At one atmosphere pressure, the molar volume of an ideal gas would be 24.465 L/mol at 25oC and 22.414 L/mol at 0oC. 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