利用滴定曲线方程和Origin精确绘制滴定曲线*

滴定曲线是滴定分析原理的重要内容。它显示了滴定过程中平衡体系性质的变化,可以获知化学计量点和滴定突跃信息,从而指导准确滴定判别或指示剂的选择。滴定曲线方程是滴定过程中体系的某种性质X(例pH)与滴定分数a(或滴定剂体积V)的关系方程,解析方程可获得函数X=f(a)的表达式。对一些较复杂的体系,推导函数X=f(a)较困难,但多数情况下反函数a=g(X)的推导更容易,表达式也更简洁。本文对酸碱、配位、氧化还原和沉淀滴定曲线方程进行了系统总结,并对不同情况下的函数X=f(a)或反函数a=g(X)进行了推导,拓展了教材内容。根据函数关系,在Origin中利用其函数绘图功能可直接绘制出滴定曲线,不用先生成数据点再绘图,方便快捷。用反函数绘图时增加数据点即可获得高精度的滴定曲线,可直接从滴定曲线上查找化学计量点和滴定突跃信息。

Plotting Titration Curves Accurately with Origin Using Titration Curve Equations

Titration curve is an important part of titration analysis principle.It shows the change of the nature of the equilibrium system in the process of titration,and the information of the stoichiometric point and the titration jump can be obtained,so as to guide the accurate titration and indicator selection.The titration curve equation is the relationship between the certain nature X(e.g.pH)of the system and the titration fraction a(or the titrant volume V)in the titration process,and after analyzing the equation the expression of the function X=f(a)can be obtained.For some complex systems,it is difficult to deduce the function X=f(a),but in most cases the inverse function a=g(X)is easier to deduce and the expression is more concise.In this paper,the equations of acid-base,coordination,redox and precipitation titration curves are systematically summarized,and the function X=f(a)or inverse function a=g(X)under different conditions are deduced,which expands the content of the textbook.According to the function,the titration curve can be directly plotted with Origin by function plotting,which is convenient and fast without producing the data points.The high-precision titration curve can be obtained by adding data points when plotting with the inverse function,and the information of the stoichiometric point and the titration jump can be found directly from the titration curve.