Now, if we multiply and divide we get about zero point 25 moles. Now, this is the number of moles and we know inside 1 mol we have abogandro number of molecules and so to find number of molecules we take this many moles multiplied by avogadro's number 6.2 times ten to 23 molecules per mole the moles cancel and we're left with about 1.51 times ten to the 23 molecules. So this is the number of molecules that are exchanged by our lungs every single minute assuming that the individual is at rest. Now, what's the point of calculating this value? Well, it was basically to show you that our lungs are capable of exchanging a great number of different molecules and although most of these molecules are oxygen and nitrogen molecules, a good portion of these are actually harmful particles such as pollutants, contaminants, allergens. They can also be viruses and bacterial cells and this can cause a problem because our lungs creates a barrier, a boundary between the outside and the internal environment.