# Diffusion coefficient for dilute gases

## Description

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## Variables

D | Diffusion coefficient (m^{2}*s^{-1}) |

N | Number of particles (dimensionless) |

V | Volume (m^{3}) |

σ | The collision cross section (m^{2}) |

k | Boltzmann constant |

T | The Absolute temperature (K) |

π | pi |

m | The molecular mass m (kg) |