Diffusion rate depends on temperature and molar mass per Graham's law

Steps:

• Graham's law states diffusion rate ∝ 1/√M, where M is molar mass; N₂ (M=28) diffuses faster than O₂ (M=32).
• From kinetic theory, diffusion rate also ∝ √T, so higher temperature increases rate.
• At same pressure, compare rates: rate ∝ √(T/M).
• Calculate relative rates: B (N₂, 323K) > A (N₂, 298K) > D (O₂, 323K) > C (O₂, 298K).

Why B is correct:

• Nitrogen at 50°C has lowest M and highest T, maximizing √(T/M) per Graham's law.

Why the others are wrong:

• A: Same gas as B but lower T reduces rate.
• C: Heavier gas than B at lower T slows diffusion.
• D: Same T as B but heavier gas decreases rate.

Final answer: B