The pressure contributed by a single gas in a mixture of different gases is called its?

• A. Dalton's Law
• B. Partial pressure
• C. Total pressure
• D. Entropy

Answer: (B)

In a gas mixture, each component exerts its own pressure as its molecules collide with the container walls. The pressure contributed by a single gas is its partial pressure—the pressure it would exert if it occupied the container alone at the same temperature and volume. In the mixture, the partial pressure of a gas equals its mole fraction times the total pressure: P_i = x_i P_total, where x_i is the mole fraction of that gas. The total pressure is the sum of all partial pressures: P_total = Σ P_i. Entropy is unrelated to how pressure is partitioned among the gases, so it doesn’t describe this concept. If you have more of a given gas in the mixture, its mole fraction and thus its partial pressure increase proportionally, while the others change accordingly.