$CO_2(g) , CO(g)$ 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 :
$H_2O(l) \rightarrow H^+(aq) + OH^-(aq)\,;\,\,\Delta H = 57.32\,kJ$
$H_2(g)+ \frac{1}{2} O_2(g) \rightarrow H_2O(l)\,;\,\, \Delta H=-286.20\,kJ$
${C_{\left( {graphite} \right)}} + {O_{2\left( g \right)}} \to C{O_{2\left( g \right)}}\,;\,\Delta H = -393.5\,kJ$
${C_2}{H_{4\left( g \right)}} + 3{O_{2\left( g \right)}} \to 2C{O_{2\left( g \right)}} + 2{H_2}{O_{\left( l \right)}}\,;\,\Delta H = - 1410.9\,kJ$
${H_{2\left( g \right)}} + 1/2{O_{2\left( g \right)}} \to {H_2}{O_{\left( l \right)}}\,;\,\Delta H = - 285.8\,kJ$
$(I)$ ${H_2}(g) + \frac{1}{2}{O_2}(g) \to {H_2}O(l);$
$\Delta {H^o_{298\,K}} = - 285.9\,kJ\,mo{l^{ - 1}}$
$(II)$ ${H_2}(g) + \frac{1}{2}{O_2}(g) \to {H_2}O(g);$
$\Delta {H^o_{298\,K}} = - 241.8\,kJ\,mo{l^{ - 1}}$
તો પાણીની મોલર બાષ્પાયન એન્થાલ્પી .....$kJ\,mol^{-1}$
[ઉપયોગ : $\left.{R}=8.3 \,{~J} \,{~mol}^{-1}\, {~K}^{-1}\right]$