If a breath of air has a volume of 1.02L at a pressure of 750 Torr and 37°C, calculate the number of molecules of air in the breath.

Use PV = nRT and solve for n = number of mols. Then n^6.0E23 = number of molecules but I think this may be sort olf a fictitious answer. I think you can use 29 as the molar mass of air.