Meaning and Measurability of Single-Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials
Meaning and Measurability of Single-Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials
复制标题
单离子活性的意义和可测量性、pH 的热力学基础以及不同材料之间离子转移的吉布斯自由能
作者：
A. Rockwood
考虑到浓度和蒸汽压之间的关系（或浓度和逸度之间的关系），单离子活度系数可以用纯热力学术语定义。测量过程涉及测量溶液和外部电极之间的接触电势。接触电势可以通过使用化学可逆过程来测量。将方程外推到零浓度和离子强度，可以确定单离子活度系数。单离子活动可以定义和测量，而不使用任何额外的热力学假设，概念或测量。该方法可作为验证超热力学方法测定单离子活度的金标准。此外，它将pH值的概念置于物理上坚实的基础上。接触电势测量也可用于确定不同材料之间离子转移的吉布斯自由能。
Considering the relationship between concentration and vapor pressure (or the relationship between concentration and fugacity) single-ion activity coefficients are definable in purely thermodynamic terms. The measurement process involves measuring a contact potential between a solution and an external electrode. Contact potentials are measurable by using thermodynamically reversible processes. Extrapolation of an equation to zero concentration and ionic strength enables determination of single-ion activity coefficients. Single-ion activities can be defined and measured without using any extra-thermodynamic assumptions, concepts, or measurements. This method could serve as a gold standard for the validation of extra-thermodynamic methods for determining single-ion activities. Furthermore, it places the concept of pH on a thermodynamically solid foundation. Contact potential measurements can also be used to determine the Gibbs free energy for the transfer of ions between dissimilar materials.