What is defined as the sum of all partial pressures in a mixture of gases?

The correct answer, total pressure, is defined as the sum of all partial pressures in a mixture of gases. In any gas mixture, each gas contributes to the overall pressure based on its individual partial pressure, which is the pressure that gas would exert if it occupied the entire volume of the mixture by itself, at the same temperature. Total pressure accounts for all the gases in the mixture, reflecting the cumulative effect of their individual partial pressures.

In practice, when dealing with air conditioning and refrigeration systems, understanding total pressure is crucial for calculations involving gas laws, phase changes, and thermodynamic processes. This concept is foundational in HVAC science, as it aids in predicting how different gases behave when mixed, particularly in situations where mixtures are subjected to various temperature and pressure conditions.