已知:
①2H2(g)+O2(g)═2H2O(l)△H1=﹣571.6kJ•mol﹣1
②CH4(g)+ O2(g)═CO(g)+2H2(g)△H2=﹣36kJ•mol﹣1
③CH4(g)+H2O(g)═CO(g)+3H2(g)△H3=+216kJ•mol﹣1