### Key Concepts and Summary

Gaseous atoms and molecules move freely and randomly through space. Diffusion is the process whereby gaseous atoms and molecules are transferred from regions of relatively high concentration to regions of relatively low concentration. Effusion is a similar process in which gaseous species pass from a container to a vacuum through very small orifices. The rates of effusion of gases are inversely proportional to the square roots of their densities or to the square roots of their atoms/molecules’ masses (Graham’s law).

### Key Equations

$rate\;of\;diffusion=\frac{amount\;of\;gas\;passing\;through\;an\;area}{unit\;of\;time}$ |

$\frac{rate\;of\;effusion\;of\;gas\;A}{rate\;of\;effusion\;of\;gas\;B}=\frac{\sqrt{m_B}}{\sqrt{m_A}}=\frac{\sqrt{ℳ_B}}{\sqrt{ℳ_A}}$ |