Enthalpies of combustion of graphite, hydrogen and acetic acid are -393 kJ/mole, -286 kJ/mole and -873 kJ/mole respectively. Enthalpy of formation ( in kJ/mole) of acetic acid would be

$$\begin{gathered} \mathrm{Given}.... \\ \mathrm{C}+{\mathrm{O}}_2\to {\mathrm{CO}}_2, ∆\mathrm{H}=-393 \mathrm{kJ}...\left(1\right) \\ {\mathrm{H}}_2+\frac{1}{2}{\mathrm{O}}_2\to {\mathrm{H}}_2\mathrm{O}, ∆\mathrm{H}=-286 \mathrm{kJ}...\left(2\right) \\ {\mathrm{CH}}_3\mathrm{COOH}+2{\mathrm{O}}_2\to 2{\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}, ∆\mathrm{H}=-873 \mathrm{kJ}...\left(3\right) \\ \mathrm{Required} \mathrm{equation} \mathrm{is} 2\mathrm{C}+2{\mathrm{H}}_2+{\mathrm{O}}_2\to {\mathrm{CH}}_3\mathrm{COOH}, ∆\mathrm{H}=? \\ ∆\mathrm{H}=\mathrm{Eq} \left(1\right)\times 2 +\mathrm{Eq}\left(2\right)\times 2 -\mathrm{Eq}\left(3\right) \\ ∆\mathrm{H}=-786-572-\left(-873\right) \\ ∆\mathrm{H}=-485 \mathrm{kJ} ; \end{gathered}$$