Mass of helium, mHe=4g Mass of oxygen, mO=32g Helium is a monoatomic gas. ∴ Degrees of freedom, f1=3 Oxygen is a diatomic gas. ∴ Degrees of freedom, f2=5 4g helium contains N1=NA=6.023×1023 number of molecules 32g oxygen contains N2=NA number of molecules. (As atomic mass of oxygen is 16g ) ∴