Practice question

**Ideal gas equation** P V = n R T = (m/M) R T, density ρ = m/V = P M/(R T), molecular mass M (kg/mol), P pressure (Pa), T temperature (K). At given P,T density proportional to M, heavier gases denser, e.g., at 1.5 atm 300 K V=24 L n= P V/(R T)=1.5×1.013×10⁵×0.024/(8.314×300)≈1.46 mol. P = (ρ R T)/(M), M = (ρ R T)/(P).P = 2 × 1.01 × 10⁵ = 2.02 × 10⁵ Pa.M = (1.2 × 8.31 × 400)/(2.02 × 10⁵) = 0.01975 kg/mol = 19.75 g/mol ≈ 20 g/mol . Substituting values gives 20 g/mol, which matches expected kinetic theory result, confirming