Given the following information, what is the heat of formation of methane?

C(s) + O2 (g) --> CO2 (g) Delta H = -94.1 kcal/mol

H2 (g) + 1/2 O2 (g)--> H2O (l) Delta H = -68.3 kcal.mol

CO2 (g) + 2H2O --> 2 O2 (g) + CH4 (g) Delta H = 212.8 kcal.mol

I realize the next step is to get the "mother" equation, but when you get that, do you have to balance the equation leaving you with..

C + 2H2 --> CH4?

Thus the Delta Hf ~ -20?

Correct answer: -17.9

C(s) + O2 (g) --> CO2 (g) Delta H = -94.1 kcal/mol

H2 (g) + 1/2 O2 (g)--> H2O (l) Delta H = -68.3 kcal.mol

CO2 (g) + 2H2O --> 2 O2 (g) + CH4 (g) Delta H = 212.8 kcal.mol

I realize the next step is to get the "mother" equation, but when you get that, do you have to balance the equation leaving you with..

C + 2H2 --> CH4?

Thus the Delta Hf ~ -20?

Correct answer: -17.9