Rate of Effusion Calculator (Graham's Law)

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Select which quantity you want to find. Graham's Law can be rearranged to solve for any variable.
Molar mass of the first gas in grams per mole. H₂ = 2.016, He = 4.003, O₂ = 32.00.
g/mol
Molar mass of the second gas in grams per mole. O₂ = 32.00, N₂ = 28.01, CO₂ = 44.01.
g/mol
Rate ratio (r₁ / r₂)
3.984

How many times faster Gas 1 effuses compared to Gas 2

Time ratio (t₁ / t₂)0.251
Gas 1 speed vs Gas 2298.4%
Gas 1 relative speed3.98397085952242
Gas 2 relative speed1

Gas 1 effuses 298.4% faster than Gas 2.

  • The rate ratio r₁/r₂ = 3.9840: for every molecule of Gas 2 that passes through the aperture, 3.98 molecules of Gas 1 pass through.
  • The time ratio t₁/t₂ = 0.2510: if Gas 2 takes a reference time, Gas 1 takes 0.2510 times as long to effuse the same volume.
  • Gas 2 is heavier (31.998 g/mol vs 2.016 g/mol) and so effuses more slowly, consistent with kinetic-molecular theory.

Next stepGraham's Law assumes ideal-gas behavior at the same temperature and pressure. At high pressures or very low temperatures, intermolecular forces cause real-gas deviations.

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