Oxygen in the Lungs: In the lungs, the respiratory membrane separates tiny sacs of air (pressure1.00x105Pa) from the blood in the capillaries. These sacs are called alveoli. The average radius of the alveoli is 0.125 mm, and the air inside contains 14% oxygen. Assuming that the air behaves as an ideal gas at 310 K, discover the number of oxygen molecules in one of these sacs.