Diffusion rates depend on molar mass and temperature

Steps:

• Apply Graham's law: diffusion rate is inversely proportional to the square root of molar mass.
• Calculate molar masses: methane (CH₄) is 16 g/mol, carbon dioxide (CO₂) is 44 g/mol, so methane diffuses faster.
• Note temperature effect: higher temperature increases average kinetic energy, speeding up diffusion for both gases.
• Conclude the fastest diffusion combines the lighter gas (methane) with high temperature.

Why B is correct:

• Matches Graham's law (methane's lower mass) and kinetic molecular theory (high temperature maximizes rate).

Why the others are wrong:

• A: CO₂ diffuses slower than methane; low temperature reduces rate.
• C: CO₂ diffuses slower than methane despite high temperature.
• D: Methane diffuses faster, but low temperature is not the most rapid condition.

Final answer: B