1. The problem statement, all variables and given/known data The standard heat of formation of n butane cannot be measured directly but can be determined indirectly from other heats of reaction by applying hess's law. Given the folowing data for the combustion of carbon hydrogen and n butane in oxygen: C + O2---> CO2 H=-393.5 H2 + 1/2O2 --> H2O C4H10 + 6.5O2 ---> 4CO2 + 5H2O 2. Relevant equations 3. The attempt at a solution Tried several times on scratch paper. The formation of butane is as so : 4C + 5H2-->C4H10 Ive tried the actual formation using CO2 + H2O --> C4H10 But i cant cancel the carbons Sticking with my other normal equation 4C + 5H2 --> C4H10 (This is what I want, No?) Tell me if my equation is wrong, cause it proabably is. I tried multiplying the first step by 4, the second step by 5, and reversing the third step only to get everything to cancel except the oxygen. I get stuck with 6.5 oxygens on the left side and 9.5 Oxygens on the right. Dont know where to g ofrom there. Help please!