Abstract: A universal thermodynamic model which can be applied to calculate mass action concentrations of components in strong electrolyte aqueous solutions has been developed in this work based on the ion-molecule coexistence theory. To verify the new universal thermodynamic model, four binary systems, such as KCl-H2O, CsCl-H2O, NaCl-H2O and BaCl2-H2O, are chosen to calculate mass action concentrations of components in a concentration range from 0.2 mol/kg to saturation level at 298.15 K. The present calculated mass action concentrations are based on pure species as standard state and mole fraction as concentration unit. A transformation coefficient is provided to convert the reported activities based on infinite dilution as standard state and mass mole fraction as concentration unit, so that the comparison of the present model with the literature data can be conducted. The transformation coefficients change in a very narrow fluctuation range for each component. The mass action concentrations of components are in good agreement with those of reported activities. Hence, the newly developed universal thermodynamic model can be successfully applied to predict activities of components in other strong electrolyte aqueous solutions and to describe their structure characteristics in aqueous solutions.

Key words: mass action concentration, activity, electrolyte aqueous solution, coexistence theory, transformation coefficient

摘要： 利用离子-分子共存理论建立了可计算强电解质水溶液组元质量作用浓度的热力学通用模型. 以KCl-H2O, CsCl-H2O, NaCl-H2O及BaCl2-H2O二元系为示例，计算了上述4个二元系在温度为298.15 K、质量摩尔浓度在0.2 mol/kg到饱和浓度范围内的组元质量作用浓度. 热力学模型计算的以纯物质为标准态、以摩尔分数为浓度单位的组元质量作用浓度经过转换后，与文献报道的以无限稀为标准态、以质量摩尔浓度为浓度单位的组元活度可良好吻合. 这说明本工作建立的强电解质水溶液的质量作用浓度热力学模型可用于预测组元活度，基于强电解质水溶液中存在离子和分子结构的推断是合理的，质量作用浓度在计算的组元浓度范围内遵守质量作用定律.

关键词: 质量作用浓度, 活度, 电解质溶液, 共存理论, 转换系数