Given, ${C_{\left( {{\rm{graphite}}} \right)}} + {O_2}\left( g \right) \to C{O_2}\left( g \right);$ <Br> $\begin{array}{l} {\Delta _r}H^\circ = - 393.5\,kJ\,mo{l^{ - 1}}\\ {H_2}\left( g \right) + \frac{1}{2}{O_2}\left( g \right) \to {H_2}O\left( l \right);\\ {\Delta _r}H^\circ = - 285.8\,kJ\,mo{l^{ - 1}}\\ C{O_2}\left( g \right) + 2{H_2}O\left( l \right) \to C{H_4} + 2{O_2}\left( g \right);\\ {\Delta _r}H^\circ = - 890.3\,kJ\,mo{l^{ - 1}} \end{array}$ <Br> Based on the above thermochemical equations, the value of ${\Delta _r}H^\circ $ at 298 K for the reaction, ${C_{\left( {{\rm{graphite}}} \right)}} + 2{H_2}\left( g \right) \to C{H