1.
Given:

C(graphite)+O2(g)→CO2(g)C(graphite) + O_2(g) \rightarrow CO_2(g); ΔH∘=−393.5\Delta H^\circ = -393.5 kJ mol−1^{-1}

H2(g)+12O2(g)→H2O(l)H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l); ΔH∘=−285.8\Delta H^\circ = -285.8 kJ mol−1^{-1}

CO2(g)+2H2O(l)→CH4(g)+2O2(g)CO_2(g) + 2H_2O(l) \rightarrow CH_4(g) + 2O_2(g); ΔH∘=+890.3\Delta H^\circ = +890.3 kJ mol−1^{-1}

Based on the above thermochemical equations, the value of ΔH∘\Delta H^\circ at 298 K for the reaction C(graphite)+2H2(g)→CH4(g)C(graphite) + 2H_2(g) \rightarrow CH_4(g) will be: