The Ideal Gas Law (sometimes called the General Gas Law) incorporates all the proportionalities of the individual gas laws we have looked at in one convenient package. It provides us, in the most practical sense, with a way to determine the number of moles in a sample of gas--something that is often impractical to determine from mass because of the low density of gases at normal room conditions.

Despite its utility, however, the law incorporates the assumptions of kinetic theory concerning the nature of gases. Of principal concern to us in using the law are these two:

gases consist of "point masses" with negligible individual volume
there are no attractive or repulsive forces among gas particles

Such a gas is described as "ideal". No such gases exist. However, under ordinary conditions of temperature and pressure, many gases exhibit behavior that is sufficiently ideal to allow us to use this law for routine work.