化学键能的大小怎样比较

2024-12-03 02:33:13
推荐回答(2个)
回答1:

主要考虑键的类型和成键双方电负性差别。

1、三键-双键-单键一般渐弱。

2、电负性差越大一般键能越大。

键能是化学键形成时放出的能量或化学键断裂时吸收的能量,可用来标志化学键的强度。它的数值是这样确定的:对于能够用定域键结构满意地描述的分子,所有各键的键能之和等于这一分子的原子化能。键能是从定域键的相对独立性中抽象出来的一个概念,它的定义中隐含着不同分子中同一类型化学键的键能相同的假定。实验证明,这个假定在一定范围内近似成立。例如,假定C─C和C─H键的键能分别是346和411千焦/摩,则算出来的饱和烃的原子化能只有2%的偏差。

键能与物质本身的关系:键能越大,本身能量就越低,键能越小,本身能量越高。做为反应物的物质,在反应过程中需要吸热,产生上述原因是因为:能量低,本身结构稳定,需要吸收更多的热量,键能大。能量高,本身结构不稳定,需要吸收的热量低,键能小。

回答2:

原子半径越短,共用电子对越多,键长越短,键能越大. 吸热反应生成物键能小于反应物键能;放热反应生成物键能大于反应物键能。共价键键能大于离子键键能大于氢键键能。

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