$\therefore X +\frac{1}{2} O _2 \longrightarrow \frac{1}{2} X _2 O \quad \Delta H =-91$
$\therefore 4 X + O _2 \longrightarrow 2 X _2 O \quad \Delta H =-90 \times 4=-360$
$CO_{(g)} + \frac{1}{2} \,O_{2(g)}\rightarrow CO_{2(g)}$ અચળ તાપમાન અને દબાણ
$\Delta H_f^o\left( {CO} \right) = - 110.5\,kJ\,mo{l^{ - 1}};$
$\Delta H_f^o\left( {C{O_2}} \right) = - 393.5\,kJ\,mo{l^{ - 1}}$