题目

—I can't get the book on the shelf. —Why not have someone tall enough  ________ it then? A. to take       B. take      C. taking      D. takes    答案：B加热N2O5依次发生的分解反应为：①N2O5(g) N2O3(g)+O2(g)      ②N2O3(g)  N2O(g)+O2(g)在容积为2 L的密闭容器中充入8 mol N2O5，加热到t ℃,达到平衡状态后O2为9 mol，N2O3为3.4 mol。则平衡体系中N2O5的物质的量浓度为A．1.8mol/LB．0.9 mol/LC．2.3 mol/LD．4.0 mol/L