1. The problem statement, all variables and given/known data CxHy gets burned in oxygen gas and makes CO2 and water. Given the partial pressure of water and the total pressure of the resulting mixture I need to find the empirical formula. 2. Relevant equations Well PV=nRT is the obvious choice...but all the information you see there is all that's given. The only other thing I was able to find was the pressure of the CO2 just doing some subtraction. The problem doesn't state a volume, temperature or anything else. Can I assume that temperature is a constant and eliminate it? How about volume? I'm not sure about that, if I can then it might help.