大学化学 >> 2023, Vol. 38 >> Issue (8): 170-176.doi: 10.3866/PKU.DXHX202208028

化学实验 上一篇    下一篇

草酸钙结晶沉淀条件对白云石中钙含量测定的影响

刘天骐1, 柳毅杰1, 宋天威1, 梁东升1, 姚奇志1,2,*()   

  1. 1 中国科学技术大学化学与材料科学学院，合肥 230026
    2 化学国家级实验教学示范中心(中国科学技术大学)，合肥 230026
  • 收稿日期:2022-08-05 录用日期:2022-10-07 发布日期:2022-11-18
  • 通讯作者: 姚奇志 E-mail:qzyao@ustc.edu.cn
  • 基金资助:
    安徽省高等学校省级质量工程教研项目(2021jyxm1730);安徽省高等学校省级质量工程教研项目(2021xxkc205);中国科学技术大学研究生教育创新计划教学改革研究项目(2020ycjg04);中国科学技术大学本科质量工程项目(2020xjyxm066);中国科学技术大学本科质量工程项目(2020xy1kc011);中国科学技术大学本科质量工程项目(2021xjyxm080);首批教育部虚拟教研室(大学化学实验课程群虚拟教研室)

Influence of Calcium Oxalate Precipitation on Determination of Calcium Content in Dolomite

Tianqi Liu1, Yijie Liu1, Tianwei Song1, Dongsheng Liang1, Qizhi Yao1,2,*()   

  1. 1 School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026, China
    2 National Demonstration Center for Experimental Chemistry Education (University of Science and Technology of China), Hefei 230026, China
  • Received:2022-08-05 Accepted:2022-10-07 Published:2022-11-18
  • Contact: Qizhi Yao E-mail:qzyao@ustc.edu.cn

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摘要：

“高锰酸钾法测定白云石中钙含量”是训练学生综合实验能力的经典分析化学实验，包括白云石矿样的溶解，草酸钙沉淀的制备和洗涤，高锰酸钾溶液浓度的标定和草酸钙沉淀的滴定。因实验过程复杂，影响因素多，学生常常为如何把测定误差控制在3‰以内而犯难。为此，我们指导学生在不同实验条件下，从溶解的白云石矿样溶液中沉淀草酸钙，研究草酸钙沉淀的颗粒大小和表面形貌与钙含量测定结果之间的关系，揭示影响钙含量测定准确度的控制因素。不仅加深了学生对实验过程的了解，而且激发了他们对化学实验学习的兴趣，提升了实验能力，增强了科研自信心。

关键词: 高锰酸钾法, 氧化还原滴定, 草酸钙, 形貌, 滴定误差

Abstract:

"Determination of calcium content in dolomite by potassium permanganate method" is a classical analytical chemistry experiment to train students' comprehensive experimental ability, including dissolution of dolomite ore sample, preparation and washing of calcium oxalate precipitate, concentration calibration of potassium permanganate solution and titration of calcium oxalate precipitate. Because of the complexity of the experiment process and the many influence factors, it is very difficult that students control the measurement error within 3‰ in the experiment. Therefore, we guide students to precipitate calcium oxalate from acid-dissolved dolomite solution under different experimental conditions, investigate the relationship between the particle size and surface morphology of calcium oxalate precipitate and the determined calcium contents, and thus revealing the control factors affecting the accuracy of calcium content determination. It not only deepens the students' understanding to the experimental process, but also stimulates their interest in learning chemical experiments, improving their experimental ability and strengthening their confidence in scientific research.

Key words: Potassium permanganate method, Redox titration, Calcium oxalate, Morphology, Titration error