Question

A. A person’s lungs can hold 6.0 L (1 L = 10-3 m3) of air at body temperature (310 K) and atmospheric pressure (101 kPa). Given that air is 21% oxygen, find the number of oxygen molecules in the lungs. [Ans: 3.0 x 1022]

B. (Continued from the previous question) If the person now climbs to the top of a mountain, where the air pressure is half that at the base, does the number of molecules in the lungs change? If so, what is the number of oxygen molecules in the lungs?

Answer 1

A.

From the Ideal Gas law,

Number of Moles =

where R is universal Gas constant, = 8.314 J/molK

Substituting,

Number of Oxygen molecules,

B.

Yes , number of molecules in the lungs change because there is not enough pressure to push the molecules effectively to the lungs.

So now pressure, half the initial pressure,

New Number of Moles =  

Number of Oxygen molecules,