Question

Why is ideal gas law important?

Answer 1

The ideal gas law is an "equation of state" that describes the relationship between pressure (`P`), density (`n/V`) and temperature (`T`). If you know any two of these quantities, you can calculate the third by rearranging the expression `PV=nRT`.

The theory behind the ideal gas law is that gas molecules undergo perfectly elastic (kinetic energy-conserving) collisions in a container of fixed volume, in which they take up none of the available space. Even though this might seem odd, for many gases this is a very good approximation, at least at high temperatures and low densities.

For highly accurate work, it is necessary to develop other, more complicated, equations of state to calculate pressures, densities and/or temperatures with high accuracy. But for most gases under most conditions, the ideal gas law can get the correct answer to within about 1% accuracy.