For a particular isomer of C8H18, The following reaction produces 5093.7 KJ of heat per mole of C8H18 (g) consumed under standered conditions. What is the standard enthalpy of formation of this isomer of C8H18 (g) ?

02 (g) = 0 kj/mol

CO2 (g) = - 393.5 kj/mol

H20 (g) = - 241.8 kj/mol

H total = - 5094 kJ

5094kJ = [8 (-393.5) + 9 (-241.8) ] - [X + 12.5 (0) ]

-5094 kJ = [-3148 + (-2176.2) ] - [x + 0]

-5094 kJ = - 5324.2 - x

add - 5324.2 to - 5094

to get + 230.2 = - x

move the negative to the other side

and you get - 230 kj/mol