If an air mixture contains 80% nitrogen and 20% oxygen at sea level, what will the partial pressure of nitrogen be at 20 meters/66 feet in sea water?

To determine the partial pressure of nitrogen in the air mixture at a depth of 20 meters (66 feet) in seawater, it is essential to understand how water pressure increases with depth and how to calculate the partial pressures of gases.

At sea level, the atmospheric pressure is approximately 1 bar (or 1 ata). As a diver descends in seawater, the pressure increases due to the weight of the water above. The pressure increases by about 1 bar for every 10 meters of depth in seawater. Therefore, at a depth of 20 meters, the pressure exerted by the water would be approximately 2 bar (1 bar from the atmosphere at the surface and 2 bar from the water).

Now, since 80% of the air mixture is nitrogen, the partial pressure of nitrogen can be calculated by multiplying the total pressure at that depth (which is 3 bar: 1 bar from the atmosphere + 2 bar from the water) by the percentage of nitrogen in the air mixture.

Calculating it out: Partial pressure of nitrogen = Total pressure at depth × Percentage of nitrogen = 3 bar × 0.80 = 2.4 bar

This calculation reveals that the partial pressure of