Introduction to the Ideal Gas Law

James Richard Fromm

Combination of the three empirical gas laws pV = k, V = k'T, and V = k"n described in the preceding three sections on Boyle's Law, Charles' Law, and Avagodro's Hypothesis leads to the ideal gas law which is usually written as

pV = nRT

The constant R in this equation is known as the universal gas constant. It arises from a combination of the proportionality constants in the three empirical gas laws. The universal gas constant has a value which depends only upon the units in which the pressure and volume are measured. The best available value of the universal gas constant is 8.3143510... J/mol K, or 8.3143510... kPa L/mol K. Another value which is sometimes convenient is 0.08206... L atm/mol K. The litre (L) is exactly 1000 mL and exactly 1/1000 of a cubic metre, so these values can be used with both large and small volumes of gases.

Copyright 1997 James R. Fromm