Which principle explains why the mass of a gas affects its rate of diffusion and effusion?

• A. Charles's law, which relates volume and temperature at constant pressure.
• B. Graham's law, which states that the rate of effusion is inversely proportional to the square root of the molar mass.
• C. Dalton's law, which describes the partial pressures of gases in a mixture.
• D. Boyle's law, which relates pressure and volume at constant temperature.

Answer: (B)

Verified step by step guidance

1. Identify the key concept in the question: it asks about how the mass of a gas affects its rate of diffusion and effusion.
2. Recall that diffusion and effusion describe the movement of gas particles: diffusion is the spreading of gas particles through space, and effusion is the passage of gas particles through a tiny opening without collisions.
3. Understand that the rate of diffusion and effusion depends on the speed of gas particles, which is influenced by their molar mass (mass of one mole of gas particles).
4. Recognize that Graham's law mathematically relates the rate of effusion (or diffusion) to the molar mass of the gas, stating that the rate is inversely proportional to the square root of the molar mass: \(\text{Rate} \propto \frac{1}{\sqrt{M}}\) where \(M\) is the molar mass.
5. Conclude that Graham's law explains why lighter gases diffuse and effuse faster than heavier gases, making it the correct principle for this question.