7. (05江苏4.)氢气(H2)、一氧化碳(CO)、辛烷(C8H18)、甲烷(CH4)的热化学方程式分别为:
H2(g) + 1/2O2(g)
= H2O(l);△H= -285.8 kJ/mol
CO(g) + 1/2O2(g)
= CO2(g);△H= -283.0 kJ/mol
C8H18(l)
+ 25/2O2(g) = 8CO2(g) + 9 H2O(l);△H= -5518 kJ/mol
CH4(g)
+ 2 O2(g) = CO2(g) + 2 H2O(l);△H= -890.3 kJ/mol
相同质量的H2、CO、C8H18、CH4完全燃烧时,放出热量最少的是
A.H2(g)
B.CO(g)
C.C8H18(l)
D.CH4(g)