303 K时KI在CH3OH-H2O混合溶剂中活度系数研究

用电动势法测定了KI在甲醇含量为0%、20%、60%、100%的甲醇-水混合溶剂中的电动势,用幂级数展开方法、扩展的Debye-Hückel方程及Pitzer方程关联不同溶剂组成下电动势的实验值,得到电池的标准电动势E°和KI在混合溶剂中的活度系数。结果表明,在一定的溶剂比例下,KI的平均活度系数先随它的浓度增加而下降,经过一个最低点后上升,或者随浓度增加而单调递减。当KI浓度固定时,它的平均活度系数随溶剂中甲醇的含量增加而下降,表明KI在甲醇中有微弱的缔合。

Study on the Activity Coefficients of KI in CH3OH-H2O Mixed Solvents at 303 K

Electromotive force values of KI in the CH3OH-H2O mixed system with CH3OH contents(weight) of 0%,20%,60% and 100% respectively were measured at 303.15K.The standard cell potential of each condition and the activity coefficients of KI in the mixed solvent were obtained by associating the experimental values using power series expansion method,the extended Debye-Hückel equation and the Pitzer equation.The calculation results show that the activity coefficients of KI in CH3OH-H2O system with constant composition decrease at first then pass a minimum and increase gradually again as its concentration increases.When the KI concentration is fixed,its activity coefficients decrease with increasing the CH3OH contents in the mixture which indicates that there exists a weak association of KI in the CH3OH.