## Chapter 8

## Q. 8.11

Using Dalton’s Law: Finding Partial Pressures

Humid air on a warm summer day is approximately 20% oxygen, 75% nitrogen, 4% water vapor, and 1% argon. What is the partial pressure of each component if the atmospheric pressure is 1.0 ×10^{5} Pa ?

ANALYSIS According to Dalton’s law, the partial pressure of any gas in a mixture is equal to the percent concentration of the gas times the total gas pressure (750 mmHg). In this case

P_{total} = P_{O_{2}} + P_{N_{2}} + P_{H_{2}O} + P_{Ar}

## Step-by-Step

## Verified Solution

Oxygen partial pressure ( P_{O_{2}} ): 0.20 × 10^{5} Pa

Nitrogen partial pressure ( P_{N_{2}} ) 0.75 × 10^{5} Pa

Water vapor partial pressure ( P_{H_{2}O} ): 0.04 × 10^{5} Pa

Argon partial pressure ( P_{Ar} ): 0.01 × 10^{5} Pa

Total pressure = 1.0 × 10^{5} Pa

Note that the sum of the partial pressures must equal the total pressure (within rounding error).