According to Graham's law, the rate of diffusion of a gas is

  • A. directly proportional to its molar mass
  • B. inversely proportional to the square root of its molar mass
  • C. independent of its molar mass
  • D. proportional to the square of its molar mass

Explanation

Lighter molecules move faster at a given temperature, so hydrogen diffuses four times as fast as oxygen, whose molar mass is sixteen times greater and whose square root is four. This is the principle behind separating uranium isotopes by gaseous diffusion. The relationship holds for effusion through a small hole as well.

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