10. Molecular-Kinetic View of Dilute Gases

In this chapter, we will deal with the special characteristics of dilute substances especially those of dilute gases. In this context, the term “ideal gas” will be introduced. Subsequently, the general gas law, one of the most cited equations in physical chemistry, is deduced from experimental observations made in the seventeenth and eighteenth century (Boyle–Mariotte’s law, Charles’s law, Avogadro’s principle). Our understanding for these relationships will be deepened by an introduction to the kinetic theory of gases. We learn, for example, how this theory can be used to account for the pressure of a gas. In order to derive the distribution of particle velocities in a gas (Maxwell distribution), the concentration dependence (mass action equation) and additionally the energy dependence (excitation equation) of the chemical potential have to be considered. The last section of the chapter will show how we can glean the barometric formula and the Boltzmann distribution.