Understanding pH Curves in Acid-Base Titrations | 酸碱滴定pH曲线解读与应用

📚 Understanding pH Curves in Acid-Base Titrations | 酸碱滴定pH曲线解读与应用

An acid-base titration is a fundamental quantitative technique in chemistry, used to determine the concentration of an unknown acid or base by reacting it with a solution of known concentration. The pH curve, also called a titration curve, is a graph of the solution pH versus the volume of titrant added. It provides vital information about the equivalence point, the strength of the acid or base, and the buffering regions. Mastering the interpretation of these curves is essential for success in IB Chemistry.

酸碱滴定是化学中一种基本的定量分析技术，通过将未知浓度的酸或碱与已知浓度的溶液反应来确定其浓度。pH曲线又称滴定曲线，是溶液pH值随滴定剂加入体积变化的图像。它提供关于等当点、酸碱强度及缓冲区域的关键信息。掌握解读这些曲线对于IB化学的学习至关重要。

1. Fundamentals of Titration Curves | 滴定曲线基础

In a typical titration, a burette is filled with a titrant of known concentration, such as NaOH, and added slowly to a conical flask containing a measured volume of the analyte, such as HCl. A pH probe continuously records the pH, or an indicator is used to signal the endpoint. The data are plotted as pH against the volume of titrant added.

在典型滴定中，滴定管中装入已知浓度的滴定剂（如NaOH），缓慢滴入盛有已知体积被测液（如HCl）的锥形瓶中。用pH计连续记录pH值，或使用指示剂指示终点。数据以pH对滴定剂体积作图。

The resulting curve is generally sigmoidal (S-shaped). It begins with a gentle slope, then shows a steep vertical section called the titration jump, followed by a plateau. The centre of the vertical section is the equivalence point, where the analyte and titrant have reacted in exact stoichiometric proportions.

所得曲线通常呈S形。起始部分斜率较小，随后出现一段陡峭的垂直区间，称为滴定突跃，之后进入平台区。垂直部分的中心即等当点，此时被测物与滴定剂按化学计量比例完全反应。

Key terms include pH = -log[H⁺], pOH = -log[OH⁻], and pH + pOH = 14 at 25 °C. The acid dissociation constant Kₐ measures the strength of a weak acid, and pKₐ = -log Kₐ.

关键术语包括pH = -log[H⁺]、pOH = -log[OH⁻]以及在25 °C下pH + pOH = 14。酸解离常数Kₐ衡量弱酸的强度，pKₐ = -log Kₐ。

2. Strong Acid – Strong Base Titration Curve | 强酸强碱滴定曲线

Consider the titration of 25.00 cm³ of 0.100 mol dm⁻³ hydrochloric acid with 0.100 mol dm⁻³ sodium hydroxide. The initial pH is -log(0.100) = 1.00, since HCl is a strong acid and dissociates completely.

以25.00 cm³ 0.100 mol dm⁻³盐酸用0.100 mol dm⁻³氢氧化钠滴定为例。初始pH为-log(0.100) = 1.00，因为HCl是强酸，完全电离。

Published by TutorHao | IB Chemistry Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）