At 25°C, the enthalpy of the following processes are given: H_2( g )+ O_2( g ) → 2 OH ( g ), Δ H^°=78 kJ mol^-1; H_2( g )+1 / 2 O_2( g ) → H_2 O ( g…

At $\displaystyle 25$°C, the enthalpy of the following processes are given: $$\begin{array}{rlll} \mathrm{H}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) & \rightarrow & 2 \mathrm{OH}(\mathrm{~g}) & \Delta \mathrm{H}^{\circ}=78 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \mathrm{H}_2(\mathrm{~g})+1 / 2 \mathrm{O}_2(\mathrm{~g}) & \rightarrow & \mathrm{H}_2 \mathrm{O}(\mathrm{~g}) & \Delta \mathrm{H}^{\circ}=-242 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ \mathrm{H}_2(\mathrm{~g}) & \rightarrow & 2 \mathrm{H}(\mathrm{~g}) & \Delta \mathrm{H}^{\circ}=436 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ 1 / 2 \mathrm{O}_2(\mathrm{~g}) & \rightarrow & \mathrm{O}(\mathrm{~g}) & \Delta \mathrm{H}^{\circ}=249 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{array} $$ What would be the value of X for the following reaction? $\displaystyle \_\_\_\_$ (Nearest integer) $$\mathrm{H}_2 \mathrm{O}(\mathrm{~g}) \rightarrow \mathrm{H}(\mathrm{~g})+\mathrm{OH}(\mathrm{~g}) \Delta \mathrm{H}^{\circ}=\mathrm{X} \mathrm{~kJ} \mathrm{~mol}^{-1} $$