alleryStart learning →Graham's law states that the rate of effusion of a gas is inversely proportional to what?
AThe square root of its molar mass
BThe square of its molar mass
CThe cube root of its molar mass
DThe molar mass of the gas itself
Answer & Solution
Correct answer: A. The square root of its molar mass
1. Heavier molecules move more slowly at a given temperature, so they reach a small hole less often.
2. Graham's law puts a number on this: the rate of effusion goes as one over the square root of the molar mass.
3. For two gases, the ratio of rates is the square root of the second molar mass over the square root of the first.
4. Because the square root softens the difference, a gas sixteen times heavier effuses only four times more slowly, not sixteen times.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.4 Effusion and Diffusion of Gases_
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