Diffusion coefficient for dilute gases


Diffusivity or diffusion coefficient is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). For dilute gases, kinetic molecular theory relates the diffusion coefficient D to the particle density n = N/V, the molecular mass , the collision cross section , and the absolute temperature.

Related formulas


DDiffusion coefficient (m2*s-1)
NNumber of particles (dimensionless)
VVolume (m3)
σThe collision cross section (m2)
kBoltzmann constant
TThe Absolute temperature (K)
mThe molecular mass m (kg)