Consider the following data
Heat of combustion of H_2(g) = -241.8kJ mol^-1
Heat of combustion of C(S) = -393.5kJ mol^-1
Heat of combustion of C₂H₅OH(l) = -1234.7kJ mol^-1
The heat of formation of C₂H₅OH(l) is(-) _________ kJ mol^-1(Nearest integer)

$\begin{array}{l}{\mathrm{H}}_2+{\mathrm{O}}_2\to {\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{\ell }\right)} ; {\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{o}}=-241.8\mathrm{kJ}/\text{ mole }\\ \mathrm{C}+{\mathrm{O}}_2\to {\mathrm{CO}}_2 ; {\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{o}}=-393.5\mathrm{kJ}/\text{ mole }\\ \\ {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}+3{\mathrm{O}}_2\to 2{\mathrm{CO}}_2+3{\mathrm{H}}_2\mathrm{O}\\ \\ {\mathrm{\Delta H}}_{\text{coms }}\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)=\left[2\times {\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{CO}}_2\right)+3\times {\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{o}}\left({\mathrm{H}}_2\mathrm{O}\right)\right]-{\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{o}}\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)\end{array}$
$\begin{array}{l}-1234.7=2\times -393.5+3\times -241.8-{\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)\\ -1234.7=-787-725.4-{\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)\\ -1234.7+1512.4=-{\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)\\ 277.7=-{\mathrm{\Delta H}}_{\mathrm{f}}^0\left({\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{OH}}_5\right)\\ {\mathrm{\Delta H}}_{\mathrm{f}}^{\mathrm{o}}\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)=-278\mathrm{kJ}/\text{ mole }\end{array}$