A Theoretical Study of Oxidation-Reduction Titration Curves

[摘要] The variation of potential and completeness of reaction in an oxidation-reduction titration of Red1 (a Ox1 + n1e¡êAb Red1) by Ox2 (c Ox2 + n2e¡êd Red2) is analyzed on the basis of general expressions. It is shown that the reaction deficiency as well as the rate of variation of the potential with titration fraction change in proportion to the [n2 (a£­b)£­n1 (c£­d)] th power of the concentration of the reagents. In particular, at the equivalence point, the expression of the potential contains a concentration dependent term that is proportional to ac£­bd. Thus, the equivalence-point potential varies with the concentration of the reagents unless ac=bd is satisfied. It is also shown that the sharpness of the potentiometric end point is affected by exchanging titrand and titrant. The inflexion point of the potentiometric titration curve is shown to occur either prior to or after the equivalence point depending upon whether n1c < n2b or n1c > n2b, the deviation being the same order of magnitude as the relative deficiency at the equivalence point.

[学科分类] 化学（综合）