题目

一James didn’t show up last night, did he? 一No．He __________．We had changed our plan． A．shouldn’t have come                                   B．didn’t need to come C．needn’t have come                                      D．needn’t come 答案：B强酸与强碱的稀溶液发生中和反应的热效应：H+(aq)+ OH－(aq) → H2O (l) +57.3kJ向1L0.5mol/L的NaOH溶液中加入稀醋酸、浓硫酸、稀硝酸，则恰好完全反应时的热效应Q1、Q2、Q3的关系正确的是A．Q1 < Q2 < Q3B．Q1 > Q3 > Q2C．Q2 > Q1 > Q3D．Q1 < Q3 < Q2