What is Dalton's Law?

What is Dalton's Law?

• A. Gases mix and exert their own partial pressures independent of each other.
• B. Total gas pressure equals atmospheric pressure at sea level only.
• C. Volume and pressure are inversely related while temperature remains constant.
• D. Increasing temperature increases gas volume proportionally.

Answer: (C)

In a mixture of nonreacting gases, each gas exerts its own pressure as if it were alone in the container, and those pressures add up to the total pressure. This means the total pressure is the sum of the partial pressures of all the gases present. The partial pressure of a given gas is proportional to how much of that gas is in the mixture (its mole fraction) and to the total pressure: P_i = X_i × P_total, and P_total = P_i + P_j + P_k + …. For example, in air, nitrogen and oxygen make up most of the mixture, so their partial pressures are roughly 0.78 atm and 0.21 atm at a total pressure of 1 atm, with small amounts from other gases contributing the remainder. This additive behavior comes directly from how gas molecules distribute themselves and how pressure arises from their collisions, as described by the ideal gas relationships. The other ideas reflect different gas laws: a statement about total pressure equaling atmospheric pressure only at sea level isn’t a general rule and depends on context; a statement about volume changing inversely with pressure at constant temperature is Boyle’s law; and a statement about volume increasing with temperature at constant pressure is Charles’s law.

In a mixture of nonreacting gases, each gas exerts its own pressure as if it were alone in the container, and those pressures add up to the total pressure. This means the total pressure is the sum of the partial pressures of all the gases present. The partial pressure of a given gas is proportional to how much of that gas is in the mixture (its mole fraction) and to the total pressure: P_i = X_i × P_total, and P_total = P_i + P_j + P_k + ….

For example, in air, nitrogen and oxygen make up most of the mixture, so their partial pressures are roughly 0.78 atm and 0.21 atm at a total pressure of 1 atm, with small amounts from other gases contributing the remainder. This additive behavior comes directly from how gas molecules distribute themselves and how pressure arises from their collisions, as described by the ideal gas relationships.

The other ideas reflect different gas laws: a statement about total pressure equaling atmospheric pressure only at sea level isn’t a general rule and depends on context; a statement about volume changing inversely with pressure at constant temperature is Boyle’s law; and a statement about volume increasing with temperature at constant pressure is Charles’s law.