【摘要】 确认KCl水溶液的阴、阳离子迁移数接近,在物理化学教学方面具有重要意义,但教材并未提及测定方法。本实验设计基于国内大多物理化学实验室皆有的希托夫法实验装置,简单易行,无环境污染。然而若仅使用KCl溶液,则存在阳极区发生Cl^-被氧化析出剧毒Cl₂的环保和安全问题。对此,根据电化学氧化过程中需在电解质/电极界面失去电子的特征提出了一种双液系升级版希托夫法实验装置,即在阳极区通过盐桥串联KOH溶液,KOH溶液与阳极接触,阳极区的反应转化为OH^-在电解质/电极界面失去电子被氧化析出O₂。同时结合与物理化学实验难溶盐溶度积相关的莫尔法,通过沉淀滴定得到阴极区Cl^-浓度的变化,计算得到Cl^-、K⁺迁移数分别为0.500、0.500,验证了2者导电能力接近。本实验既是对希托夫法测定离子迁移数实验的创新,也有助于深入理解饱和KCl溶液作为盐桥和饱和甘汞参比电极工作溶液的原理,并拓宽了盐桥应用场景;还激发学生灵活运用电子传递、离子迁移、溶度积和沉淀滴定等知识进行实验设计以及自我解惑答疑的兴趣;因而,在广度和深度方面皆有助于提升物理化学实验教学水平。更多还原

【Abstract】 It is mentioned in the electromotive force experiment of the physical chemistry that the anion and cation transference number values of KCl aqueous solution are close to each other,but the method of determination is unknown.This experiment is designed to use the Hittorf’s method experimental setup,which is available in most physical chemistry laboratories in China,and is simple and easy to perform without environmental pollution.However,if only KCl solution were used,there would be an environmental and safety problem that Cl^- would be oxidized in the anode area and toxic Cl₂ would give off.This innovative experiment addresses on the above issues and proposes an upgraded two-compartment Hittorf apparatus,which is based on the essential characteristic of electron loss at the electrolyte/electrode interface during electrochemical oxidation.Besides the KCl solution,the KOH solution is connected in series via a salt bridge in the anodic region,where KOH contacts the power supply’s positive electrode.Thereby the anodic reaction is transformed into that the OH anions lose electron at the electrolyte/electrode interface to give off O₂.Moreover,the concentration change of the Cl^-in the cathodic region is obtained by precipitation titration（the Mohr’ s method）,which is related to the basic knowledge of solubility product of insoluble salts in physical chemistry.Then the transference number values of the Cl^-,K⁺ are calculated to be 0.500 and 0.500,respectively,and verified to be close to each other.This experiment not only upgrades the experiment of Hittorf’s method for determining transference number,but also provides an in-depth understanding of the principle of saturated KCl solution as a working solution for both salt bridge and saturated calomel reference electrodes,together with broadening the application scenario of salt bridge.It also triggers students’ interest in designing experiments by applying the knowledge points of standard electrode potential,solubility product,and precipitation titration.Thus,it helps to improve the experimental teaching level of physical chemistry in terms of both breadth and depth.更多还原