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

Dalton's Law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each individual gas in the mixture. This law applies under the assumption that the gases do not react with each other and that they occupy the same volume. Each gas in the mixture behaves independently, and its partial pressure is determined by its mole fraction in the mixture and the total pressure.

This principle is crucial for various applications, including diving, where understanding the behavior of gases under pressure is essential for safe practices. It allows divers to calculate the partial pressure of each gas they are breathing, which is important for managing exposure to oxygen and avoiding nitrogen narcosis or oxygen toxicity.

The other options present misunderstandings about gas behavior. The notion that only the heaviest gas contributes to the total pressure fails to recognize that all gases, regardless of their mass, exert pressure. Suggesting that all gases exert the same pressure within a mixture overlooks the concept of partial pressures and the fact that they can vary in accordance to their concentration. Lastly, stating that the volume of gases must equal the total pressure misinterprets the relationship between volume and pressure, which is governed by the ideal gas law and not directly summarized by Dalton's Law.