The ideal gas state equation is very simple, but its scope of applicability is very limited. It is desirable to have state equations that represent accurately and without limitations the P-v-T behavior of the substances in a larger region. Naturally, this class of equations is more complicated. For this purpose, several equations are known, but in this opportunity, we will study only three of them, which in my opinion are the most important. These are the following:

Van der Waals state equation.

The Van der Waals state equation was proposed in 1873, it has two constants that are determined from the behavior of a substance at the critical point, and is given by: