Practice question

**Dalton's law of partial pressures** total pressure P_total = Σ P_i, P_i = X_i P_total, X_i mole tion, each gas exerts pressure as if alone, ideal gas mixture P_i V = n_i R T, partial pressure proportional to mole tion, e.g., air 79% N₂ 21% O₂ P_N₂=0.79 atm P_O₂=0.21 atm at 1 atm total. For monatomic gas, C_v = (3)/(2) R.Heat Q = μ C_v Δ T = 1 × (3)/(2) × 8.31 × 20 = 249.3 J ≈ 249 J . Substituting values gives 249 J, which matches expected kinetic theory result, confirming mean free path λ = 1/(√2 n π d²), ideal gas