食用碱测定实验中酚酞终点问题的讨论  

Titration End Point in Determination Experiment of Edible Alkali

作　　者：刘晓庚[1] 刘琴[1] 任赛佳 刘雯 陆佳俊 张晓云 崔颖 秦福义 高然 

机构地区：[1]南京财经大学食品科学与工程学院,南京210023 [2]南京师范大学附属中学,南京210003

出　　处：《化学教育（中英文）》2018年第6期78-81,共4页Chinese Journal of Chemical Education

基　　金：江苏省高校品牌专业建设工程资助项目(PPZY2015B152);南京财经大学高教研究项目(2016020Y);南京财经大学大学生创新项目(201610327059Y)

摘　　要：食用碱的组成分析和含量测定是分析化学实验中具有开发潜力的重要实验，因此将其设计成综合设计性开放实验后遇到了很多值得探讨的问题。其中，双指示剂滴定分析中的酚酞终点问题就是一个典型的问题。通过提出问题、实验探究和理论剖析，对酚酞终点的问题进行了较透彻的分析与讨论，最终得出结论：在室温下NaHCO3溶液完全自发分解成Na2CO3、CO2和HeO，且CO2会自动逸出，滴定液放置时间过长时微红色终点会逐渐加深。教学实践表明该实验作为分析化学的设计性开放实验很适合大学低年级学有余力的学生学习。Composition analysis and content determination of edible alkali is an important ex- periment which has the developing potential in the chemical experiment, but after designing the comprehensive design of open experiment we met a lot of interesting issues. How to make sure of the end point of phenolphthalein in the double indicator titration is one of the typical problems. Through asking question, making a thorough analysis and discussing the experimental study and theoretical analysis on phenolphthalein end point problem, we finally draw the conclusion that： at room temperature, NaHCO3 solution is completely spontaneously decomposed into Na2CO3, CO2, H20 and CO2 will automatically escape, and if we store it for a long time, the red end point will gradually increase. It shows that the choice of such experiments as the comprehensive and the opening experiments is very suitable for top undergraduates in analytical chemistry.

关 键 词：食用碱 定量分析 实验教学 滴定终点颜色变化 碳酸氢钠分解 

分 类 号：G642[文化科学—高等教育学] O655.2-4[文化科学—教育学]