4.已知H2O(l)H2(g)＋O2(g)，ΔH＝285kJ/mol；C(s)＋O2(g)CO2(g)，ΔH＝－[!--empirenews.page--]394kJ/mol；CH4(g)＋2O2(g)CO2(g)＋2H2O(l)，ΔH＝－888kJ/mol