How many mols of gas are in a person's lungs with a pressure of 1.0 atmosphere, a volume of 3.5 L at a temperature of 37^oC?   <-- NOTE data has only two significant digits.

1. We are using the ideal gas equation. This is a question asking about a single state instead of a change from on condition to another.  

2. The ideal gas equation PV = nRT needs to be rearranged to solve for the number of mols.

3.         n =  PV / RT

4. list the values for the formula   

             P = 1 atm;      T  = 37^oC  + 273 = 310^oK;    R =  0.082058 L atm mol^-1 K^-1.

5. Replace the symbols with their numerical values.

             n   =  PV / RT  =   (1 atm )(3.5 L) / ( 0.0820 L atm / mol K ) (310^oK )

             n   = (3.5 / 24.42)  mols  = 0.138 mols  = 0.14 mols  rounded to two sf