Enter the Molar Mass of Gas 1 and Molar Mass of Gas 2 (or pick from the Quick Pick dropdowns) into this Rate of Effusion Calculator to find the Rate Ratio (r₁/r₂), which gas effuses faster, its Speed Factor, and — if you provide an Effusion Rate for Gas 1 — the calculated Effusion Rate of Gas 2.
Rate Ratio (r₁/r₂)
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Faster Gas
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Speed Factor
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Effusion Rate of Gas 2
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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. Lighter gases diffuse faster than heavier gases at the same temperature and pressure.
No, gases with higher molecular weight diffuse slower. According to Graham's law, the rate is inversely proportional to the square root of molar mass, so heavier molecules move more slowly.
Yes, Graham's law applies to both effusion (gas escaping through a small hole) and diffusion (gas spreading through another gas). The mathematical relationship is the same for both processes.
No, you don't need specific temperature or pressure values. Graham's law compares relative rates, and when both gases are at the same temperature and pressure, these factors cancel out in the ratio.
Use grams per mole (g/mol) for molar mass. Since Graham's law calculates ratios, the units cancel out, but consistent units are important for accurate results.
Graham's law is used in gas separation processes, uranium enrichment, determining molecular weights of unknown gases, and predicting how quickly gas leaks will spread in industrial settings.