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在滴定分析教学中常常遇到所谓滴定的可行性问题,即能够准确进行滴定的条件。如用NaOH滴定一个弱酸,这个弱酸的浓度与离解常数应符合什么条件滴定才能准确进行(本文仅讨论用指示剂目测终点的情况)。关于这个问题的结论,各教科书上虽都明确指出:弱酸能被准确(误差≤0.1％)滴定的条件是CK_a≥10~(-8)。但对于这个可行性界限的来源,众说不一。一些教科书上通过比较不同C和K_a的滴定曲线形状后,定性地得出这个结论。另一些书上通过计算一系列不同C、K_a体系的滴定突跃后列表归纳出这个结论。络合
Titration in the teaching of teaching often encountered the so-called titration of the feasibility of the problem that can accurately titration conditions. Such as titration of a weak acid with NaOH, the weak acid concentration and dissociation constant should be consistent with what conditions titration can be accurately carried out (this article only discusses the case of indicator visual endpoint). On the conclusion of this issue, although all textbooks clearly pointed out that: weak acid can be accurate (error ≤ 0.1%) titration conditions CK_a ≥ 10 ~ (-8). But the sources of this line of feasibility are different. Some textbooks conclude this qualitatively by comparing titration curve shapes of different C and K_a. Other books summed up this conclusion by calculating the list of titrations after a series of different C, K_a systems. Complex