A:H2O(g)=H2(g)+1/2O2(g)ΔH=+242kJ·mol-1
B:2H2(g)+O2(g)=2H2O(l)ΔH=-484kJ·mol-1
C:H2(g)+1/2O2(g)=H2O(g)ΔH=+242kJ·mol-1
D:2H2(g)+O2(g)=2H2O(g)ΔH=+484kJ·mol-1