Question

how does the mass, or heaviness, of a particle affect the rate of diffusion? mass only affects the rate of diffusion when the temperature is high. heavier particles typically diffuse faster than lighter particles. lighter particles typically diffuse faster than heavier particles. mass does not affect the rate of diffusion.

Explanation:

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. According to Graham's law of effusion and diffusion, the rate of diffusion of a gas is inversely proportional to the square root of its molar mass ($r\propto\frac{1}{\sqrt{M}}$). Lighter particles (with lower mass) have higher average speeds at a given temperature (from the kinetic - molecular theory, $v_{rms}=\sqrt{\frac{3RT}{M}}$ where $v_{rms}$ is the root - mean - square speed, $R$ is the gas constant, $T$ is temperature, and $M$ is molar mass). So, lighter particles diffuse faster. Mass affects the rate of diffusion at all temperatures (as long as there is thermal motion, which is true above absolute zero). Heavier particles have lower average speeds and thus diffuse more slowly.

Answer:

C. Lighter particles typically diffuse faster than heavier particles.