Avogadro’s law and gas density: proportionality with molecular mass For two gases at the same temperature and pressure, state how their densities compare with their molecular masses. Choose the correct relationship.

ConceptAt the same T and p, Avogadro’s law implies equal molar volumes. Density ρ is ρ = (mass)/(volume) = (M molar mass)/(molar volume). With constant molar volume, ρ ∝ M.

Stepρ₁/ρ₂ = M₁/M₂

Final AnswerDirectly proportional to molecular mass