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