Back in class we had the following problem:
The air we breathe is about 21% oxygen, by volume. Exhaled air contains about 14% of oxygen. The absorption of oxygen within the lungs takes place in tiny spherical compartments called alveoli which have a diameter of the order of 0.1 mm. Estimate the number of oxygen molecules absorbed in one breath in each of the alveoli. (Assume that body temperature is 37°C.)
n= \frac{pV}{RT}= \frac{101325 Jm^{-3}\times 5.23\times 10^{-13}m^{3}}{8.3145JK^{-1}mol^{-1}\times 310.15K}
n=2.06\times 10^{-11} mol
N= 1.24\times 10^{-13} molecules
I assumed that the pressure inside the alveoli is 1 atm, that r= \frac{d}{2} and calculated the volume using V= \frac{4}{3} r^{3} \pi
Now, 21 \% - 14 \% = 7\% and 7 \% \times N= 8.7 \times 10^{11} End-of-chapter solution is 6.9 \times 10^{12}molecules
What am I doing wrong?
@admin: It seems to me now that this should better be in the general Chemistry thread?