Particle number density n (cm-3)
According to the kinetic gas theory the number n of the gas molecules, referenced
to the volume, is dependent on pressure p and thermodynamic
temperature T as expressed in the following:
p = n · k · T (1.1)
n = particle number density
k = Boltzmann’s constant
At a certain temperature, therefore, the pressure exerted by a gas depends
only on the particle number density and not on the nature of the gas. The
nature of a gaseous particle is characterized, among other factors, by its
mass mT.
Gas density ρ (kg · m-3, g · cm-3)
The product of the particle number density n and the particle mass mT is
the gas density ρ:
ρ = n · mT (1.2)
The ideal gas law
The relationship between the mass mT of a gas molecule and the molar
mass M of this gas is as follows:
M = NA · mT (