What does Dalton's Law state about the total pressure of a gas mixture?

What does Dalton's Law state about the total pressure of a gas mixture?

• A. The total pressure of a mixture of gases equals the sum of the pressures of the gases in the mixture.
• B. The pressure of a gas is independent of its partial pressure.
• C. Only the strongest gas contributes to total pressure.
• D. Pressure cannot be predicted for gas mixtures.

Answer: (A)

Each gas in a mixture contributes its own partial pressure, and the total pressure is the sum of these partial pressures. In an ideal gas mixture, a gas exerts the same pressure it would exert if it alone filled the container, and all these independent pressures add up to the overall pressure. So if you know how much of each gas is present (their mole fractions or amounts) and the total pressure, you can relate them by Pi = xi P for each component, and Ptotal = P1 + P2 + P3 + … . This perspective helps explain everyday air and other gas mixtures: the total pressure is simply the sum of the pressures from nitrogen, oxygen, argon, carbon dioxide, and so on, each contributing according to how abundant it is. The idea holds best for ideal gases and under conditions of relatively low pressure and moderate temperature; real gases show small deviations at high pressures or very low temperatures, but the additive nature of the pressures is the guiding principle.

Each gas in a mixture contributes its own partial pressure, and the total pressure is the sum of these partial pressures. In an ideal gas mixture, a gas exerts the same pressure it would exert if it alone filled the container, and all these independent pressures add up to the overall pressure. So if you know how much of each gas is present (their mole fractions or amounts) and the total pressure, you can relate them by Pi = xi P for each component, and Ptotal = P1 + P2 + P3 + … .

This perspective helps explain everyday air and other gas mixtures: the total pressure is simply the sum of the pressures from nitrogen, oxygen, argon, carbon dioxide, and so on, each contributing according to how abundant it is. The idea holds best for ideal gases and under conditions of relatively low pressure and moderate temperature; real gases show small deviations at high pressures or very low temperatures, but the additive nature of the pressures is the guiding principle.