I am reading through a thesis paper and it says that for a combustion process in which we have separated the chamber into 2 zones: burned and unburned ideal gas mixtures, if we know the pressure and equivalence ratio (ER) for the unburned ideal gas mixture, we can find all of its thermodynamic properties. Doesn't the ER just allow us to find the number of moles of each species? And thus knowing pressure and ER (moles) we are still left with two unknowns (Tunburned and Vunburned) in the ideal gas relation: pV = nRT. Am I missing the obvious here? Any thoughts are appreciated.