$CO_2(g) , CO(g)$ અને $H_2O(g)$ માટે $\Delta H^o_f$ના મૂલ્યો અનુક્રમે $-393.5, -110.5$ અને $-241.8\, kJ/mol$,
$CO_2(g) + H_2(g) \to CO(g) + H_2O(g)$ is :
\(\Delta {H^o} = [\Delta H_f^o(CO)(g) + \Delta H_f^o({H_2}O)(g)] - \)
\([\Delta H_f^o(CO)(g) + \Delta H_f^o({H_2})(g)]\)
\( = [ - 110.5 + ( - 241.8)] - [ - 393.5 + 0]\)
\( = 41.2\,kJ\)