Acid-base titration is the most basic experiment in analytical chemistry.The titration curve reflects the whole process of neutralization reaction and is very important to understand acid-base titration.Based on three basic hypotheses, the chemical equilibrium, electroneutrality principle and mass balance, we established mathematical model between ionization degree and pH as well as titration percentage by keeping one parameter unchanged and the other two changed at the initial point.In addition, we recovered the acid-base titration curve by performing mathematical analysis and derivatization of the function.Through the analysis of two initial conditions in mathematical formula and the effects on the function, the quantitative validation on interpretations was introduced for reactions of different concentrations and strength of acids in titrations described in traditional teaching materials.With theoretical expansion of titration curves, we proposed a possible method for weak acid titration.

In the acid-base titration curve of titration from NaOH to HAc, shown in the sixth edition of Analytical Chemistry edited by Wuhan University, we found that there was an obvious protruding part of the curve at the initial stage of titration, which was significantly different from the curve of titration from NaOH to HCl at the same concentration. In this paper, the mathematical expression of fitting the curve is derived by using various equilibrium relations in acid-base reaction. The correlation law of acid-base titration is proved by combining with the image of mathematical function. The mathematical model can explain not only the differences between two curves, but also the reasons and influencing factors of the initial titration curve difference of weak acids by strong alkali titration.