Which of the following best defines the partial pressure of a gas in a mixture?

• A. The pressure exerted by the gas only when it is the most abundant component in the mixture.
• B. The pressure that the gas would exert if it alone occupied the entire volume at the same temperature.
• C. The pressure exerted by the gas divided by the number of moles of all gases present.
• D. The total pressure exerted by all gases present in the mixture.

Answer: (B)

Verified step by step guidance

1. Understand that the partial pressure of a gas in a mixture refers to the pressure that gas would exert if it were alone in the container at the same temperature and volume.
2. Recall Dalton's Law of Partial Pressures, which states that the total pressure of a gas mixture is the sum of the partial pressures of each individual gas.
3. Recognize that the partial pressure of a gas depends on its mole fraction in the mixture and the total pressure, given by the formula: \(P_i = X_i \times P_{total}\), where \(P_i\) is the partial pressure of gas \(i\), \(X_i\) is its mole fraction, and \(P_{total}\) is the total pressure.
4. Note that the partial pressure is not related to whether the gas is the most abundant component; it depends on its proportion and the total pressure.
5. Conclude that the best definition of partial pressure is: 'The pressure that the gas would exert if it alone occupied the entire volume at the same temperature.'