"Calculate the internal energy for the air in human lungs after a regular inhalation. You find this volume discussed in the context of the spirometer (textbook p. 203). Hint: treat air as an ideal gas with the molecular mass M = 29.00 g/mol "
Not sure the process to solve this?
Knowing the molecular mass is not enough for the internal energy. You need to know that it is a diatomic gas, for which the molar specific heat at constant volume (Cv) is (3/2)R
The internal energy is
U = Cv*n*T = (3/2)*n*R*T
T is the absolute temperature, 310K inside the body.
n is the number of moles in the lungs, which is PV/RT
U = (3/2)*P*V
Look up the spirometer lung volume V and use 1.01*10^5 N/m^2 (1 atm) for P