Calculate the standard enthalpy of formation of `CH_(3)OH(l)` from the following data:
(1) `CH_(3)OH(l)+(3)/(2)O_(2)(g)toCO_(2)(g)+2H_(2)O(l),Delta_(r)H^(0)=-726kJ*mol^(-1)`
(2) `C(s)+O_(2)(g) to CO_(2)(g),Delta_(c)H^(0)=-393kJ*mol^(-1)`
(3) `H_(2)(g)+(1)/(2)O_(2)(g)toH_(2)O(l),Delta_(f)H^(0)=-286kJ*mol^(-1)`.

Explanation

To get the formation reaction for `CH_(3)OH(l)`, we combine three thermocheical equations provided in the given way:
`C(s)+O_(2)(g)+2[H_(2)(g)+(1)/(2)O_(2)(g)]-CH_(2)OH (l)-(3)/(2)O_(2)(g)toCO_(2)(g)+2H_(2)O(l)-CO_(2)(g)-2H_(2)O(l)`,
`DeltaH^(0)=[-393+2(-286)-(-726)]kJ*mol^(-1)`
or, `C(s)+2H_(2)(g)+(1)/(2)O_(2)(g)toCH_(3)OH(l),`
`DeltaH^(0)=-239kJ*mol^(-1)` . . [1]
Eq. [1] represents formation reaction of `CH_(3)OH(l)`. so, standard enthalpy of formation is `-239kJ*mol^(-1)`.