What is the partial pressure of O2 at 165 fsw according to Dalton's law?

To determine the partial pressure of oxygen (O2) at a depth of 165 feet of seawater (fsw) using Dalton's Law of Partial Pressures, we first need to understand the concept of partial pressure and how it applies to gases in a diving context. According to this law, the total pressure of a gas mixture is equal to the sum of the partial pressures of each component gas in the mixture.

At sea level, the atmospheric pressure is approximately 1 ata (atmosphere absolute), which includes the weight of the atmosphere as well as the pressure exerted by the water column when diving. In seawater, approximately every 33 feet of depth adds about 1 ata of pressure due to the water column.

To calculate the total pressure at 165 fsw:

1. 1 ata (surface pressure) + (165 fsw / 33 feet) ata = 1 ata + 5 ata = 6 ata

Now, considering the composition of the atmosphere, about 21% of it is oxygen. Therefore, to find the partial pressure of O2 at 165 fsw:

2. Partial pressure of O2 = Total pressure * Fraction of O2 in the air

3. = 6