搜题请搜索小程序“爱下问搜题”
问题 选择题

下列有关σ键和π键的说法错误的是

A．在某些分子中，化学键可能只有π键而没有σ键

B．当原子形成分子时，首先形成σ键，可能形成π键

C．一般情况下，同一个分子中的σ键比π键更稳定些

D．含有π键的分子在反应时，π键是化学反应的积极参与者

答案

答案：A

单键全部是σ键，双键是由1个σ键和1个π键形成的，三键是由1个σ键和2个π键形成的，所以选项A不正确，其余都是正确的，答案选A。

阅读理解

小题1:Why did the BeauxArts style attract American entrepreneurs?

A．It helped display their money status.

B．It was created by famous architects.

C．It was named after a famous institute.

D．It represented the 19th century urban culture.小题2:What is unique of SieMatic BeauxArts?

A．Its designs are anti-conventional.

B．Its designs come from famous structures.

C．Its customers can enjoy their own composition.

D．Its customers can choose from various new styles.
查看答案
单项选择题

室外覆盖用直放站输入、输出电压驻波比是：（）

A.≤1.5

B.≤1.4

C.≤1.2

D.≤1.0
查看答案