Graham's law

Graham's law states that, under the same conditions, a gas’s effusion rate is inversely proportional to the square root of its molar mass.

Effusion: Effusion is the escape of gas molecules through a tiny opening into a lower-pressure region. Graham's law quantifies how quickly gases effuse through the same opening.
Isotope separation: Isotope separation enriches a material in one isotope relative to others. Small mass differences create small effusion-rate differences that can be exploited over many stages.
Ideal gas law: The ideal gas law relates pressure, volume, amount, and temperature through PV = nRT. It supplies the gas-state relationships often used when comparing effusion experiments.
Fick's laws of diffusion: Fick's laws describe how diffusive flux depends on concentration gradients and their changes over time. They model ordinary diffusion, not the molecular escape measured by effusion.
Kinetic theory of gases: The kinetic theory explains gas properties through the motion and collisions of microscopic particles. At equal temperature, gases have similar average molecular kinetic energy, linking mass to speed.
Gaseous diffusion: Gaseous diffusion separates gas components by exploiting differences in their molecular speeds through porous barriers. It applies Graham's mass-dependent transport principle across repeated barrier passages.
Temperature: Temperature measures the thermal state of a system and determines the average kinetic energy of its particles. The rate comparison assumes gases are at the same temperature.
Viscosity: Viscosity measures a fluid's resistance to flow and deformation. Bulk gas flow through an opening can depend on viscosity, unlike ideal molecular effusion.
Root-mean-square speed: Root-mean-square speed is the square root of the mean squared speeds of particles in a system. Its inverse-square-root dependence on molar mass underlies the rate ratio.
Uranium enrichment: Uranium enrichment increases the proportion of uranium-235 relative to uranium-238. Historical gaseous-diffusion plants used the isotopes' slight mass difference to enrich uranium hexafluoride.

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