Diffusion coefficient (Mass diffusivity) for 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). The dependence of the diffusion coefficient on temperature for gases can be expressed using Chapman–Enskog theory.

Related formulas


Ddiffusion coefficient (cm^2/s) (dimensionless)
Tabsolute temperature (K) (dimensionless)
M1molar mass molecule 1 (g/mol) (dimensionless)
M2molar mass molecule 2 (g/mol) (dimensionless)
ppressure (atm) (dimensionless)
σ12average collision diameter (Å) (dimensionless)
Ωtemperature-dependent collision integral (dimensionless) (dimensionless)