Chemistry - Thermochemistry Question with Solution | TestHub

(i)$\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to \mathrm{C}{\mathrm{O}}_2\left(\mathrm{g}\right)\mathrm{\Delta }\mathrm{H}=-\mathrm{393.5 }\mathrm{k}\mathrm{J}$
(ii)$\mathrm{C}\mathrm{O}\left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{O}}_2\left(\mathrm{g}\right)\to \mathrm{C}{\mathrm{O}}_2\left(\mathrm{g}\right)\mathrm{\Delta }\mathrm{H}=-\mathrm{283.0 }\mathrm{k}\mathrm{J}$
eq. (i) and (ii) gives
(iii)$\mathrm{C}(s)+\frac{1}{2}{\mathrm{O}}_2(\mathrm{g})\to \mathrm{C}{\mathrm{O}}_{}(\mathrm{g})\mathrm{\Delta }\mathrm{H}=-\mathrm{110.5 }\mathrm{k}\mathrm{J}$
This equation (iii) also represents formation of one mole of CO and thus enthalpy change is the heat of formation of CO (g).