Questions on Diffusion, Effusion, and Graham’s Law
Diffusion, Effusion, and Graham’s Law – Multiple Choice Questions
1. What is diffusion?
A) The compression of a gas
B) The passage of gas through a tiny hole
C) The movement of gas molecules from high to low concentration
D) The boiling of a liquid
E) The reflection of gas particles
2. What is effusion?
A) Expansion of gases in a container
B) Movement of molecules across a membrane
C) Passage of gas through a tiny hole without collisions
D) Gases dissolving in liquids
E) Rapid movement of gases under pressure
3. Graham’s Law compares:
A) Gas densities and volumes
B) Rates of diffusion and molar masses
C) Boiling points of gases
D) Compressibility of solids
E) Temperatures and volumes
4. What is the formula for Graham’s Law?
A) P₁V₁ = P₂V₂
B) r₁/r₂ = √(M₂/M₁)
C) PV = nRT
D) V = kT
E) r = d × t
5. Which gas diffuses faster: helium (4 g/mol) or oxygen (32 g/mol)?
A) Oxygen
B) Both at same rate
C) Helium
D) Cannot be determined
E) Depends on volume
6. According to Graham’s Law, the lighter the gas, the:
A) Slower it diffuses
B) Faster it effuses
C) More it condenses
D) Higher its boiling point
E) More mass it has
7. If gas A has a molar mass of 16 g/mol and gas B has a molar mass of 64 g/mol, how many times faster does A effuse than B?
A) 2
B) 4
C) 1
D) 8
E) √2
8. Which gas would effuse slowest?
A) H₂ (2 g/mol)
B) He (4 g/mol)
C) CH₄ (16 g/mol)
D) O₂ (32 g/mol)
E) Xe (131 g/mol)
9. Graham’s Law works best when gases:
A) React chemically
B) Are at very high pressures
C) Behave ideally and are at the same temperature
D) Are liquids
E) Are under a vacuum
10. In diffusion, gas molecules move from:
A) Low to high concentration
B) Low to low pressure
C) High to low concentration
D) Equilibrium to saturation
E) Hot to cold instantly
11. If gas A effuses 3 times faster than gas B, what is the molar mass ratio (M_B / M_A)?
A) 3
B) 9
C) 1
D) 1/9
E) √3
12. Which factor does not affect diffusion rate?
A) Temperature
B) Mass of the gas
C) Volume of the container
D) Concentration gradient
E) Molecular size
13. Effusion is most closely modeled in which real-world example?
A) Gas bubbling in water
B) Perfume spreading in a room
C) Air leaking through a puncture in a tire
D) Ice melting
E) Water vapor condensing
14. Graham’s Law is based on which principle?
A) Laws of Thermodynamics
B) Avogadro’s Law
C) Kinetic Molecular Theory
D) Dalton’s Law
E) Law of Conservation of Mass
15. A gas with molar mass 36 g/mol effuses in 30 seconds. How long would it take a gas of 144 g/mol to effuse under the same conditions?
A) 60 s
B) 90 s
C) 120 s
D) 15 s
E) 30 s
16. Gases at the same temperature have:
A) Equal masses
B) Equal effusion rates
C) Equal average kinetic energies
D) Equal volumes
E) Equal diffusion times
17. In Graham’s Law, the ratio of rates is inversely proportional to the square root of:
A) Volume
B) Temperature
C) Molar mass
D) Pressure
E) Density
18. Which condition increases the rate of diffusion?
A) Decreasing temperature
B) Increasing molecular weight
C) Decreasing volume
D) Increasing temperature
E) Increasing molar mass
19. Two gases at the same temperature have molar masses of 28 and 4 g/mol. What is the diffusion rate ratio (r₁/r₂)?
A) 1
B) √(4/28)
C) √(28/4)
D) 28/4
E) 2
20. Which pair of gases would diffuse at nearly the same rate?
A) O₂ (32 g/mol) and CO₂ (44 g/mol)
B) H₂ (2 g/mol) and He (4 g/mol)
C) CO (28 g/mol) and N₂ (28 g/mol)
D) Cl₂ (71 g/mol) and Ar (40 g/mol)
E) CH₄ (16 g/mol) and SO₂ (64 g/mol)
- Questions on Molar Mass of a Gas
- Questions on Dalton’s Law of Partial Pressures
- Questions on Mole Fraction
Answers with Full Explanations
1. C – Diffusion is movement of gas from high to low concentration.
2. C – Effusion is passage of gas through a tiny hole without collisions.
3. B – Graham’s Law compares rate of diffusion or effusion to molar mass.
4. B – r₁/r₂ = √(M₂/M₁), where r is rate and M is molar mass.
5. C – Helium is lighter → diffuses faster than oxygen.
6. B – The lighter the gas, the faster it effuses.
7. A – r₁/r₂ = √(64/16) = √4 = 2 times faster.
8. E – Xenon (131 g/mol) is heaviest, so effuses slowest.
9. C – Works best with ideal gases at same T.
10. C – Diffusion moves from high to low concentration.
11. B – r₁/r₂ = 3 → M₂/M₁ = 9.
12. C – Volume of container doesn’t directly affect diffusion rate.
13. C – Effusion is best modeled by air leaking from a tire.
14. C – Graham’s Law is derived from the Kinetic Molecular Theory.
15. C – Time₂ = Time₁ × √(M₂/M₁) = 30 × √(144/36) = 30 × 2 = 60 s
16. C – At same temperature, gases have equal average kinetic energy.
17. C – r ∝ 1 / √M, inverse square root of molar mass.
18. D – Higher temperature increases kinetic energy → faster diffusion.
19. C – r₁/r₂ = √(28/4) = √7
20. C – CO and N₂ both have molar mass ~28 g/mol → diffuse at same rate.
Share Online!
