Given C(graphite)+O2(g)→CO2(g);ΔrH∘=−393.5kjmol−1H2(g)+12O2(g)→H2O(l);ΔrH∘=−285.8kjmol−1CO2(g)+2H2O(l)→CH4(g)+2O2(g);ΔrH∘=+890.3kJmol−1 Based on the above thermochemical
equations, the value of ΔrH∘ at 298K for the reaction C(graphite)+2H2(g)→CH4(g) will be