University Chemistry ›› 2019, Vol. 34 ›› Issue (2): 49-54.doi: 10.3866/PKU.DXHX201806014

• Chemistry Laboratory • Previous Articles     Next Articles

Improving Experiment on Determining the Empirical Formula of Hexamine Cobalt(Ⅲ) Chloride: Measuring the Chlorine Content by Potentiometric Titration

Zhou WANG,Jianxin SHI*(),Min PENG,Saili ZHENG,Lianyun LI,Rong LAI,Kejia ZHU   

  • Received:2018-06-15 Published:2019-02-26
  • Contact: Jianxin SHI E-mail:cessjx@mail.sysu.edu.cn
  • Supported by:
    2017年中山大学校级质量工程项目“重点教材建设项目”

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Abstract:

The experiment on preparation and empirical formula determination of hexamine cobalt(Ⅲ) chloride is a comprehensive experiment in the basic chemistry laboratory. The coordination compound was prepared by the reaction of CoCl2 with H2O2 as the oxidant, excess ammonia and NH4Cl with the catalysis of activated carbon. The empirical formula of the product was obtained by taking the integer of the ratio of NH3, Co and Cl based on their contents from titration. In this paper, the titration method of Cl was improved. The Cl contents from the potentiometric titration method and Mohr method were compared. Results show that the potentiometric titration method has the advantages of higher precision, better reproducibility and reliability, as well as the better teaching effect.

Key words: [Co(NH3)6]Cl3, Empirical formula, Mohr method, Potentiometric titration method