Amagat's Law states that the volume of a gas mixture is the sum of the pure component volumes. Which statement best reflects this?

Amagat's Law states that the volume of a gas mixture is the sum of the pure component volumes. Which statement best reflects this?

• A. Amagat's law
• B. Dalton's law
• C. Raoult's law
• D. Gibbs-Duhem relation

Answer: (A)

This question hinges on the idea that gas volumes in a mixture add up. Amagat's law says that at the same temperature and pressure, the volume of a gas mixture equals the sum of the volumes that the pure components would occupy in that same conditions, i.e., the volumes are additive through partial molar volumes: V = sum_i n_i * V̄_i. For ideal gases, every component has the same molar volume at a given T and P, so the total volume reduces to V = n_total RT/P, consistent with the ideal gas law. This additive-volume view is the essence of Amagat's law. The other laws describe different properties: Dalton's law concerns partial pressures summing to total pressure, Raoult's law addresses vapor pressures in solutions, and the Gibbs–Duhem relation ties together changes in chemical potentials with composition.

This question hinges on the idea that gas volumes in a mixture add up. Amagat's law says that at the same temperature and pressure, the volume of a gas mixture equals the sum of the volumes that the pure components would occupy in that same conditions, i.e., the volumes are additive through partial molar volumes: V = sum_i n_i * V̄_i. For ideal gases, every component has the same molar volume at a given T and P, so the total volume reduces to V = n_total RT/P, consistent with the ideal gas law. This additive-volume view is the essence of Amagat's law. The other laws describe different properties: Dalton's law concerns partial pressures summing to total pressure, Raoult's law addresses vapor pressures in solutions, and the Gibbs–Duhem relation ties together changes in chemical potentials with composition.