The correct arrangement of gases in the order of increasing rate of diffusion is [H = 1, C = 12, N = 14, O = 16, S = 32]

Analyze the question: We need to arrange gases from the slowest diffusion to the fastest diffusion.

Concept (Graham's Law of Diffusion): The rate of diffusion of a gas is inversely proportional to the square root of its molar mass:

Rate ∝ 1/√M

So the heavier the gas, the slower it diffuses. "Increasing rate of diffusion" therefore means decreasing molar mass, from heaviest to lightest.

Molar masses:

• H₂ = 2
• NH₃ = 14 + 3 = 17
• CO = 12 + 16 = 28
• N₂ = 28
• O₂ = 32
• NO₂ = 14 + 32 = 46
• CO₂ = 12 + 32 = 44
• SO₂ = 32 + 32 = 64

Check each option:

• A. CO₂ (44), H₂ (2), SO₂ (64), CO (28): The masses are not in decreasing order, so this is wrong.
• B. SO₂ (64), O₂ (32), NH₃ (17), H₂ (2): The masses decrease steadily, so the rates increase steadily. This is correct.
• C. NH₃ (17), NO₂ (46), N₂ (28), CO₂ (44): There is no consistent order, so this is wrong.
• D. CO₂ (44), NH₃ (17), O₂ (32), SO₂ (64): The order is mixed, so this is wrong.

Answer: Option B. SO₂ is the heaviest, so it diffuses slowest, and H₂ is the lightest, so it diffuses fastest.

Exam tip: For "increasing rate of diffusion" questions, just write out the molar masses and look for the option where they go from largest to smallest. Remember: light gases are fast, heavy gases are slow. H₂ is nearly always the fastest gas in JAMB options.