物理化学学报 >> 2005, Vol. 21 >> Issue (12): 1384-1389.doi: 10.3866/PKU.WHXB20051211

研究论文 上一篇    下一篇

盐酸在硫酸镁水溶液中的Harned规则

吕兴梅;王琴萍;赵桂贞;陈树森;吕殿祯   

  1. 沈阳师范大学化学与生命科学学院, 沈阳 110032；辽宁大学化学系, 沈阳 110036
  • 收稿日期:2005-06-16 修回日期:2005-07-22 发布日期:2005-12-15
  • 通讯作者: 吕殿祯 E-mail:ludianzhen@yahoo．com．cn

Harned’s Rule of HCl in Magnesium Sulfate Solutions

LÜ Xing-Mei;WANG Qin-Ping;ZHAO Gui-Zhen;CHEN Shu-Sen;LÜ Dian-Zhen   

  1. College of Chemistry and Life Science, Shenyang Normal University, Shenyang 110032; Department of Chemistry, Liaoning University, Shenyang 110036
  • Received:2005-06-16 Revised:2005-07-22 Published:2005-12-15
  • Contact: LÜ Dian-Zhen E-mail:ludianzhen@yahoo．com．cn

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摘要： 在盐酸-硫酸镁-水三元系混合介质中, 以标准H2电极和Ag-AgCl电极组成无液接电池, 应用经典的电动势(EMF)方法测定下列电池的电动势： Pt, H2 (101.325 kPa )│HCl (m＝0.01000 mol·kg-1)│AgCl-Ag (A) Pt, H2 (101.325 kPa)│HCl (mA), MgSO4 (mB), H2O│AgCl-Ag (B) 根据电池(A)得到Ag-AgCl电极在278.15、288.15、298.15、308.15和318.15 K等5个温度时纯水中的标准电极电势. 对电池(B)恒定体系总离子强度I为 0.2、0.4、0.6、0.8、1.0、1.5 mol·kg-1, 硫酸镁的离子强度分数yB恒定为 0.00、0.10、0.20、0.30、0.50和0.70, 测定电池(B)在278.15、288.15、298.15、308.15和318.15 K等5个温度时的电动势. 由于体系中存在硫酸的二级解离, 采用数学迭代方法确定平衡体系中氢离子的浓度, 根据测得电池(B)的电动势数据计算了混合溶液中盐酸的活度系数γA. 结果表明: 在溶液中总离子强度保持恒定时, 盐酸的活度系数服从Harned规则, 在组成恒定时混合物中HCl的活度系数lgγA对热力学温度T作图是一条直线. 进一步讨论了混合溶液中盐酸的相对偏摩尔焓．

关键词: 盐酸, EMF, 活度系数, 硫酸镁, Harned规则

Abstract: Many chemical and biochemical phenomena take place in solution, making the evaluation of solvent effects a critical element for understanding these phenomena. The effect of the solvent on activity coefficients of electrolytes was of interest to chemists and chemical engineers because it may provide useful information. In this paper the thermodynamic properties of HCl-MgSO4-H2O system have been studied by EMF (electromotive force) measurement in the cells without liquid junction Pt, H2 (101.325 kPa )│HCl (m＝0.01000 mol·kg-1)│AgCl-Ag (A) Pt, H2 (101.325 kPa )│HCl (mA), MgSO4 (mB) , H2O│AgCl-Ag (B) at constant total ionic strength I=0.2, 0.4, 0.6, 0.8, 1.0, 1.5 mol·kg-1 and yB=0, 0.10, 0.20, 0.30, 0.50, 0.70 at different temperatures from 278.15 to 318.15 K. Because of secondary dissociation of sulfuric acid in the system, the concentrations of hydrogen ions in equilibrium system have been determined by mathematic iterative technique. The standard electrode of AgCl-Ag in pure water has been determined according to the method of Bates. The activity coefficients of HCl lgγA in the HCl-MgSO4-H2O system have been determined from cell (B). The results show that the activity coefficients of HCl in the solutions still obey Harned’s rule and lgγA is a linear function of the absolute temperature at constant composition of the mixture.

Key words: Hydrochloric acid, EMF, Activity coefficients, Magnesium sulfate, Harned’s rule