Haw is the diffusion of molecules affected by changes in molecular weight? Molecules with lower molecular weight diffuse faster than molecules with high molecular weight. Molecules with higher molecular weight diffuse faster if the temperature is decreased. Molecular weight does not affect the diffusion of a gas. Molecules with lower molecular weight diffuse faster if the temperature is increased.

The correct statement is: **Molecules with lower molecular weight diffuse faster than molecules with high molecular weight.**<br /><br />This is because diffusion is influenced by the kinetic energy of the molecules, which is related to their mass and velocity. According to Graham's law of effusion, the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. Therefore, lighter molecules (with lower molecular weight) will diffuse more quickly than heavier molecules.