If propane with specific parameters were to combust in open air, what is actual volume of CO2 produced Lets say we have a sample of propane gas having a volume of 2.70 L at standard room temperature and 1.75 atm. This gas is exposed to our air. The equation that governs this reaction is:

$mC_3H_8 + xO_2 + 3.76xN_2 \rightarrow yCO_2 + zH_2O + dN_2 + eO_2$ 

Here $m,x,y,z,d$ and $e$ are coefficients. I want to find out what the volume of carbon dioxide given this information. The trouble I'm having is finding out what pressure the air is and I strongly suspect that I would use the sea level or 1 atm and the volume of nitrogen and oxygen with which propane reacts with.
Rephrased homework question? Anyway, you are going about this the wrong way, thinking much too complicated.

If you combust m moles of propane, how many moles y of CO2 do you get? Now remember that moles and liters of ideal gas are totally proportional, and you have the answer.