1. The problem statement, all variables and given/known data A sample of a hydrocarbon is combusted completely in O2(g) to produce 19.65gCO2(g), 4.023gH2O(g), and 280kJ of heat. Calculate the value of ΔH∘f per empirical-formula unit of the hydrocarbon. 2. Relevant equations None I know of 3. The attempt at a solution Previous calculations found that the hydrocarbon had a mass of 5.811g. Per empirical formula unit: (I determined the empirical formula to be CH, which was correct) molar mass of CH = 13.018g/mol 5.811g / 13.018g/mol = 0.447 mol CH 280kJ/0.447 mol = 627.266 kJ/mol My final answer was 627.266 kJ/mol but that was not correct. Am I interpreting the meaning of "empirical-formula unit" correctly? Any help is greatly appreciated.