Okay, I'm keeping an open mind about this. I was cr@p at thermodynamics at college, but something I do remember is that the Mole is an atomic or molecular parameter - i.e. it applicable only to atoms of pure gases, so as far as I know you cannot relate it directly to a mixture of gases like air. It can be defined as the number of atoms needed such that the number of grams of a substance equals the atomic mass of the substance.
As far as I can see, for Ian to work in Moles he would need to know how much a "mole of air" weighted to convert N back to kg. I had a look about and reckon its 28.964 grams per mole. I should be able to use R in J/mol/K and then use this to convert at the end, but I'm going for a curry in a minute.
But R is the Gas Constant. It is the measure of energy in a unit amount of a gas per degree, therefore it shouldn't change with temperature or pressure, rather energy changes are determined by it. While writing this I have come across another similar value for R for air of 287.05 Joule/Kg/K. If it does change with temperature and pressure then it is foolish for the sites I pulled this off to call it "R" - it should be called something else.
Anyway it all seemed to work when I layed it out, but as your freind correclty points out I only used one temperature / pressure point so it might all go to hell if either of these figures change.
I'm not dissing what your mate says. If he works in chemistry then I'm sure he's forgotten more about moles than I will ever know, but I'm not quite ready to say I got it wrong yet.