Amagat's Law states which of the following?

• A. The volume of a gas mixture equals the sum of the pure component volumes measured at the same temperature and pressure.
• B. The pressure of a gas mixture equals the sum of partial pressures.
• C. The temperature of a gas mixture equals the average of component temperatures.
• D. The mass of a gas mixture equals the sum of component masses.

Answer: (A)

Amagat's law describes additive volumes in an ideal gas mixture. It says the total volume of the mixture at a given temperature and pressure equals the sum of the volumes each pure component would occupy if it were alone at that same temperature and pressure. This follows from the ideal gas relation V = nRT/P for each component, so V_total = sum of V_i, where each V_i = n_i RT/P. In other words, each gas contributes its own volume at the mixture’s T and P, and those volumes add up.

This is distinct from Dalton’s law, which deals with pressures: the total pressure is the sum of the partial pressures. The other statements—temperature being an average of component temperatures or the mass simply adding—don’t capture how volumes combine in a gas mixture under the ideal-gas assumption.