AEMCA Practice Exam

According to Dalton's Law, how is atmospheric gas pressure determined?

1. By the volume of gas present

2. By the sum of all partial pressures

3. By the temperature of the gas

4. By the density of the gas

The correct answer is: By the sum of all partial pressures

Dalton's Law states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas in that mixture. This means that each gas contributes to the overall pressure in proportion to its amount and its individual pressure, which is determined by its specific conditions of temperature and volume. In a real-world context, this principle is crucial for understanding how gases behave in the atmosphere, as the presence of different gases (like nitrogen, oxygen, carbon dioxide, etc.) all contribute to the atmospheric pressure we measure. Therefore, option B accurately reflects Dalton’s Law by emphasizing that the total atmospheric pressure is the sum of the pressures exerted by each gas in the atmosphere, affirming the validity of this law in explaining gas behavior. The other options—relating to the volume, temperature, or density of the gas—do not encapsulate the essence of Dalton's Law and instead focus on other physical properties that do not account for the additive pressure contributions of different gases in a mixture. Hence, the correct understanding of atmospheric gas pressure, as defined by Dalton's Law, centers around the summation of partial pressures rather than these other factors.