Enthalpy of combustion - Alkanes ( PROFESSORS OR ChEM GRADS) PLease im so desperate :(?

Question

Okay so i wrote the balanced equation, and thats pretty much all i can do.. if someone can help me that would be so great.. thanks !

CH3C6H13(l) + O2(g) --> 5CO2(g) + 8H2O(l)

Write a balanced equation for the combustion of CH3C6H13(l) (methyl hexane)
-- i.e. its reaction with O2(g) forming the products CO2(g) and H2O(l).

Given the following standard heats of formation:

* deltaHf° of CO2(g) is -393.5 kJ/mol
* deltaHf° of H2O(l) is -286 kJ/mol
* deltaHf° of CH3C6H13(l) is -173.0 kJ/mol


What is the standard heat of reaction (deltaH°) for the combustion reaction of CH3C6H13(l)?

The next question is

Calculate the difference, deltaH-deltaE=delta(PV) for the combustion reaction of 1 mole of methyl hexane.
(Assume standard state conditions and 298 K for all reactants and products.)

CRAAAPPPPPPPPP I FORGOT SOMETHING

I"m SO sorry...


FOR THE BALANCED EQUATION IT'S

9O2 --->> GIVES THE REST.. so SORRY

Answer 1

The way you do it is:

Delta H = (5 x -393.5) + (8 x -286) - (-173)

Watch all the minus signs!

Now you are on your way.