Question

For each pair of gases, select the one that most likely has the highest rate of effusion. Use the periodic table if necessary.

Oxygen (O2) or hydrogen (H2):

Methane (CH4) or carbon tetrachloride (CCl4):

Nitrogen (N2) or ammonia (NH3):

Fluorine (F2) or chlorine (Cl2):

Answer 1

Use Graham’s law: rate ∝ 1/√(molar mass). The lighter gas effuses faster.

- Oxygen (O2) or hydrogen (H2): H2 (H2 is much lighter; rate ratio ≈ √(32/2) = 4 → H2 effuses ~4× faster)
- Methane (CH4) or carbon tetrachloride (CCl4): CH4 (16 vs ~154 g·mol−1; rate ratio ≈ √(154/16) ≈ 3.1)
- Nitrogen (N2) or ammonia (NH3): NH3 (17 vs 28 g·mol−1; rate ratio ≈ √(28/17) ≈ 1.28)
- Fluorine (F2) or chlorine (Cl2): F2 (38 vs ~71 g·mol−1; rate ratio ≈ √(71/38) ≈ 1.37)