大学化学 >> 2021, Vol. 36 >> Issue (8): 2009043.doi: 10.3866/PKU.DXHX202009043

师生笔谈 上一篇    下一篇

HF溶液和HF-F-溶液的多重平衡计算

张颖, 权新军()   

  • 收稿日期:2020-09-18 录用日期:2021-01-18 发布日期:2021-01-25
  • 通讯作者: 权新军 E-mail:quanxj@jlu.edu.cn
  • 作者简介:权新军, Email: quanxj@jlu.edu.cn

Multi-Equilibrium Calculations for HF Solution and HF-F- Solution

Ying Zhang, Xinjun Quan()   

  • Received:2020-09-18 Accepted:2021-01-18 Published:2021-01-25
  • Contact: Xinjun Quan E-mail:quanxj@jlu.edu.cn

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摘要：

HF溶液和HF-F-溶液中存在着HF的解离和HF与F-化合两个反应，溶液中各物种的平衡浓度都是两个平衡共同作用的产物，理论上只有将两个平衡同时考虑才能得到正确的结果。但在以往教学中对HF的解离平衡关注较多，而对HF与F-的化合平衡关注较少，造成学生在遇到这类问题时常常采取错误的计算方法。本文从培养学生应对复杂系统计算的综合能力出发，根据多重平衡原理推导出计算HF溶液和HF-F-溶液离子浓度的简便精确关系式，通过对比计算发现，除了HF溶液当其浓度小于1.91×10-2 mol·L-1时可以近似地按一元弱酸同时计算H+和F-浓度外，其他情况下都必须同时考虑两个平衡进行计算。

关键词: 氢氟酸, 解离平衡, 多重平衡, 复杂系统, 计算

Abstract:

In HF solution and HF-F- solution, there are not only the dissociations of hydrofluoric acid but also the reactions between hydrogen fluoride and fluoride ion, so the equilibrium concentration of each component is the final product of two equilibria. Theoretically, the correct result can be obtained only if the two equilibria are considered simultaneously. However, much attention has been paid to the dissociation equilibrium of HF than to the HF-F- association in teaching, as a result students are used to take the wrong calculation method when confronting such problems. In order to develop students' comprehensive abilities to deal with the calculations of complex systems, the simple and accurate formulas for calculating the ion concentrations in HF solution and HF-F- solution are derived based on multi-equilibrium. By comparison, it is found that both equilibria must be considered in all cases, except that the concentration of HF solution is less than 1.91×10-2 mol·L-1 which can be approximately calculated as monobasic weak acid.

Key words: Hydrofluoric acid, Dissociation equilibrium, Multi-equilibrium, Complex system, Calculation