$2Al + C{r_2}{O_3} \to A{l_2}{O_3} + 2Cr$
${H_2}O(g) + C(s) \to CO(g) + {H_2}(g);\,\Delta H = 131\,kJ$$CO(g) + \frac{1}{2}{O_2}(g) \to C{O_2}(g);\Delta H = - 282\,kJ$
${H_2}(g) + \frac{1}{2}{O_2}(g) \to {H_2}O(g);\,\Delta H = - 242\,kJ$
$C(s) + {O_2}(g) \to C{O_2}(g);\,\Delta H = X\,kJ$
$X$ નું મૂલ્ય ......$kJ$
[ઉપયોગ : $\left.{R}=8.3 \,{~J} \,{~mol}^{-1}\, {~K}^{-1}\right]$