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Molecular Mass and Diffusion Velocity

publish date: 2026/05/19 08:39:34.218518 UTC

volume_mute

Two distinct gases, Gas A (lightweight helium molecules) and Gas B (heavy xenon molecules), are released under identical temperature conditions at opposite ends of a sealed tube. Which gas will diffuse through the air space faster?

Gas A, because lighter molecules move at higher average velocities than heavier molecules at the same temperature.

Gas B, because heavier particles possess greater momentum to smash through blocking air molecules.

They will diffuse at identical speeds because mass does not influence fluid transport mechanics.

Neither gas will diffuse because distinct chemical elements repel one another in open space.

Correct Answer

Gas A, because lighter molecules move at higher average velocities than heavier molecules at the same temperature.

Explanation

Temperature is proportional to the average kinetic energy of a gas (\(KE = \frac{1}{2}mv^2\)). At a given temperature, both gases share the same average kinetic energy; therefore, the molecules with a smaller mass (\(m\)) must possess a higher average velocity (\(v\)) and will diffuse faster.

Reference

Basic Physics: A Self-Teaching Guide

Quizzes you can take where this question appears

Diffusion through liquids and gases