Graham's Law of Effusion

Compare the rates of effusion or diffusion for two different gases based on their molar masses.

Gas Component A

Effusion Rate (r₁)

Molar Mass (M₁)

g/mol

Gas Component B

Effusion Rate (r₂)

Molar Mass (M₂)

g/mol

Calculation Results

Enter any three values to calculate the missing parameter

About this calculator

Overview

Graham's Law states that the rate of effusion or diffusion of a gas is inversely proportional to the square root of its molar mass.

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Pro Tips

Molar mass is usually measured in g/mol.
The equation is r₁ / r₂ = √(M₂ / M₁).
Gas A and Gas B must be at the same temperature and pressure for this law to hold strictly.

Fun Facts

"Lighter gases travel faster than heavier gases at the same temperature."
"Graham's Law was used to separate uranium isotopes for the first atomic bomb."
"Effusion is the process of a gas escaping through a tiny hole into a vacuum."
"Diffusion is similar but occurs through open space rather than a tiny hole."
"Helium effuses 2.65 times faster than oxygen at the same temperature."
"The law applies to ideal gases and assumes no intermolecular attractions."
"Graham's Law explains why odors spread through a room (lighter molecules move faster)."

Formula: r₁ / r₂ = √(M₂ / M₁)