The partial pressure law requires that the sum of the partial pressures is equal to which type of pressure?

The partial pressure law, also known as Dalton's Law of Partial Pressures, states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. To understand why the correct answer is absolute pressure, it’s important to know that absolute pressure is measured relative to a complete vacuum. This means it includes the pressure of the gas mixture itself along with any external atmospheric pressures.

In diving, especially when considering the effects of depth and gas mixtures, understanding absolute pressure is critical. As divers go deeper underwater, the water column above them adds to the pressure felt. This total, or absolute pressure, is the sum of atmospheric pressure and the pressure exerted by the water above, which is essential to comprehend when calculating the partial pressures of various gases in a breathing mixture.

Thus, the total pressure that the partial pressures of the individual gases refer to is the absolute pressure experienced by the diver. This contextualizes why the answer related to absolute pressure is the most accurate when discussing the application of the partial pressure law in diving scenarios.