Ethanol can undergo decomposition to form two sets of products. If the molar ratio of ${\mathrm{C}}_2{\mathrm{H}}_4\text{ to }{\mathrm{CH}}_3\mathrm{CHO}\text{ is }8:1$ in a set of product gases, then the energy involved in the decomposition of 1 mole of ethanol is :

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(g\right) {\mathrm{C}}_2{\mathrm{H}}_4\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right);\mathrm{\Delta }{H}^{\circ }=45.54\mathrm{kJ}$ (1)

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{g}\right) {\mathrm{CH}}_3\mathrm{CHO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(g\right);\mathrm{\Delta }{H}^{\circ }=68.91\mathrm{kJ}$ (2)