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.