આથી, \(\Delta H\)\(_{reaction}\) = [\(\Sigma\)\(\Delta\)\(H_f\)\(^o\) of product - \(\Sigma\)\(\Delta\)\(H_f\)\(^o\) of reactant]
\([(2 ×\) \(\Delta\)\(H_f\)\(^o\) \(of Fe(s) + 3 \) \(\Delta\)\(H_f\)\(^o of\) \(CO_2\) \((g) -\) (\(\Delta\)\(H_f\)\(^o of\) \(Fe_2O_3(s) + 3 × \) \(\Delta\)\(H_f\)\(^o of CO_{(g)}]\)
\(-6.6 = [(2 × 0) + (3 × -94) - \) (\(\Delta\)\(H_f\)\(^o\) of \(Fe_2O_3\)\({(s)} + 3 × -26.4)] \,kcal\)
\(-6.6 = [0 - 282 - \) \(\Delta\)\(H_f\)\(^o of\) \(Fe_2O_3{(s)} + 79.2]\)
\(Fe_2O_3 (s)\) માટે \(\Delta\)\(H_f\)\(^o\) \(= -196.2 \,Kcal/mol\)
$N{H_{3(g)}}\, + \,\,\frac{3}{2}\,Cu{O_{(s)}}\, \to \,\,\frac{1}{2}\,{N_{2(g)}}\, + \,\,\frac{3}{2}{H_2}{O_{(\ell )}}\, + \,\,\frac{3}{2}\,C{u_{(s)}}.$ ......$J$
$H_2O _{(g)} + C_{(s)} = CO_{(g)} + H_{2{(g)}}$; $\Delta H = 131\, KJ$, $CO_{(g)} + \frac{1}{2}\,O_{2{(g)}} = CO_2$$_{(g)}$ ; $\Delta H = -282\, KJ,H_2$ $_{(g)}$$+ \frac{1}{2}\,O_2$$_{(g)}$ $= H_2O$$_{(g)}$; $\Delta H = - 242\, KJ, $ $C_{(s)}$ $+ O_2$ $_{(g)}$ $= $ $ CO_2$ $_{(g)}$; $\Delta$ $H = - x\,\,KJ$