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## Two Solutions of Accurate pH Calculation for HA-A Standard Buffer Solution by the Simplest Form

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Abstract

The two solutions of accurate pH calculation for HA-A standard buffer solution by the simplest form were introduced. Results from the two approaches agreed well with each other, and solution #2 was validated by examples. The calculation can improve the deduction ability of the learners and enhance their comprehensive understanding of pH computational formulas, and also be a useful supplement for current analytical chemistry textbooks.

Keywords： Standard buffer solution ; Accurate pH calculation ; Activity coefficient ; The simplest form

TANG Ming-Yu. Two Solutions of Accurate pH Calculation for HA-A Standard Buffer Solution by the Simplest Form. University Chemistry[J], 2017, 32(4): 76-78 doi:10.3866/PKU.DXHX201611005

HA-A型一般缓冲溶液计算pH的最简式为：

${\rm{PH = p}}{K_a} + \lg \frac{{{c_{{{\rm{A}}^-}}}}}{{{c_{{\rm{HA}}}}}}$

${\rm{PH = p}}{K_a} + \lg \frac{{{a_{{{\rm{A}}^-}}}}}{{{a_{{\rm{HA}}}}}}$

### 1.1 思路一

a转化为c，即a = γc，因此式(2)变换为：

${\rm{PH = p}}{K_a} + \lg \frac{{{\gamma _{{{\rm{A}}^-}}}{c_{{{\rm{A}}^-}}}}}{{{\gamma _{{\rm{HA}}}}{c_{{\rm{HA}}}}}}$

### 1.2 思路二

${\rm{p[}}{{\rm{H}}^{\rm{ + }}}{\rm{] = p}}K_a^c + \lg \frac{{{c_{{{\rm{A}}^ -}}}}}{{{c_{{\rm{HA}}}}}}$

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