## 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