Amagat's Law is best described as which statement about gas mixtures?

• A. The volume of a gas mixture is the sum of the pure component volumes
• B. The boiling points of components determine the mixture volume
• C. The total pressure equals the sum of partial pressures
• D. The density of a mixture is the sum of component densities

Answer: (A)

Amagat's law says that the volume of a gas mixture at a given temperature and pressure is the sum of the volumes that each pure component would occupy under those same conditions. In other words, imagine each component alone at the mixture’s T and P; the total volume is the sum of those individual volumes. For ideal gases, the molar volume depends only on T and P (v_m = RT/P), so the mixture volume equals the total moles times the same v_m, reinforcing the additive-volume idea. The other statements aren’t describing this volume additivity: total pressure adds up in Dalton’s law, not the volumes; and density doesn’t simply add, while boiling points don’t directly set mixture volume.