Question

【題目】N2和H2合成NH3的能量變化如圖所示，該反應的熱化學方程式是( )

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

Answer 1

【答案】B

【解析】根據能量與反應過程的關系，合成氨是放熱反應，△H<0，得出熱化學反應方程式為：1/2N2(g)＋3/2H2(g)=NH3(g) △H=(a－b)kJ·mol－1或N2(g)＋3H2(g)=2NH3(g) △H=2(a－b)kJ·mol－1，1/2N2(g)＋3/2H2(g)=NH3(l) △H=(a－b－c)kJ·mol－1或N2(g)＋3H2(g)=2NH3(l) △H=2(a－b－c)kJ·mol－1，故選項B正確。