The chemical composition of air that is exhaled (expired) is different from ordinary air. Atypical analysis of expired air at 37 °C and 1.00 atm, expressed as percent by volume, is 74.2% N₂, 15.2% O₂, 3.8% CO₂, 5.9% H₂O, and 0.9% Ar. The composition of ordinary air is given in Practice Example 6-12B.

(a) What is the ratio of the partial pressure of CO₂(g) in expired air to that in ordinary air?

(b) Would you expect the density of expired air to be greater or less than that of ordinary air at the same temperature and pressure? Explain.

(c) Confirm your expectation by calculating the densities of ordinary air and expired air at 37 °C and 1.00 atm.

Practice Example 6-12(B)

The percent composition of air by volume is 78.08% N₂, 20.95% O₂, 0.93% Ar, and 0.036% CO₂.What are the partial pressures of these four gases in a sample of air at a barometric pressure of 748 mmHg?