When a person breaths, his lungs can hold up to 5.5 Litre of air at body temperature 37^(@)C and atmospheric pressure ("1 atm = 101 kPa"). This Air contains 21% oxygen. Calculate the number of oxygen molecules in the lungs.

When a person breaths, his lungs can hold up to 5.5 Litre of air at bo

1.	When a person breaths, his lungs can hold up to 5.5 Litre of air at body temperature 37^(@)C and atmospheric pressure ("1 atm = 101 kPa"). This Air contains 21% oxygen. Calculate the number of oxygen molecules in the lungs.
Answer» Solution :We can treat the air inside the lungs as an ideal gas. To find the NUMBER of molecules, we can use the ideal gas LAW. PV = NkT Here volume is given in the Litre. 1 Litre is volume occupied by a CUBE of side 10 CM 1 Litre = 10 cm `xx` 10 cm `xx` 10 cm = `10^(-3)m^(3)` N =`(PV)/(kT) = (1.01 xx 10^(5) xx 5.5 xx 10^(-3))/(1.38 xx 10^(-23) xx 310)` = 1.29 `xx 10^(23)` Molecules Only `21%` of N are oxygen. The total number of oxygen molecules `= 1.29 xx 10^(23) xx (21)/(100)` Number of oxygen molecules = `2.7 xx 10^(22)` molecules