题目

N2和H2合成NH3的能量变化如图所示，该反应的热化学方程式是(  ) A. N2(g)＋3H2(g) ＝ 2NH3(g) ；△H ＝ 2(b—a) kJ/mol B. N2(g)＋3H2(g) ＝ 2NH3(l)；△H ＝ 2(a—b—c) kJ/mol C. N2(g)＋H2(g) ＝ NH3(l) ；△H ＝ (b＋c—a) kJ/mol D. N2(g)＋H2(g) ＝NH3(g) ；△H ＝ (a＋b) kJ/mol 答案：B

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