Gas Diffusion Rate Factors Steps:

• Recall Graham's law: diffusion rate is inversely proportional to the square root of molecular mass (rate ∝ 1/√M).
• Note from kinetic molecular theory: higher temperature increases average kinetic energy, so rate ∝ √T.
• For highest rate, minimize M (small mass) to maximize 1/√M and maximize T (high temperature) to maximize √T.
• Compare options: only C combines both favorable conditions.

Why C is correct:

• Small molecular mass increases rate via 1/√M in Graham's law; high temperature boosts kinetic energy for faster molecular movement.

Why the others are wrong:

• A: Large mass decreases rate via √M, outweighing high temperature's increase.
• B: Large mass and low temperature both decrease rate.
• D: Low temperature decreases rate despite small mass's benefit.

Final answer: C