Propane combustion
 

Dear All,

I am trying to determine what the kmol/kg for each species in the burnt prpducts of a C3H8 and Air flame are assuming one step chemistry. I need this data to use the Janaf tables. Does anyone know how I can calculate this from the Stoichiometric ratio, and assuming just C02,H20 and N2 in the products? I have seen expression such as:

C/H = 3/8 = (nCO2)/(2*nH2O), but I cannot understand how this makes sense. Where does the 2 in the denominator come from? How can we ignore the presence of 0xygen in both of these (C02 and H20)?

Thank you all.