本研究的目的是利用離子選擇性電極，量測在不同溫度下單電解質KCl、NaCl、KBr與NaBr水溶液中，個別離子的活性係數。並從這些個別的離子活性係數，計算求得電解質水溶液的平均離子活性係數。 實驗結果顯示，在單電解質水溶液中，陽離子的活性係數，與陰離子的活性係數不同。這由於離子間、及離子與溶劑間的交互作用力。而離子的活性係數，也與相反離子的性質有關。在溫度效應下，固定濃度的單電解質水溶液其離子活性係數隨著系統溫度的升高而降低。 本研究的方法，與以往汽液平衡實驗數據不同，在於以實驗方法，獲得單電解質水溶液中，個別離子的活性係數，並以此實驗數據，比較一些模式如：Chen et al. (1982)、與Pitzer (1980)，探討之間的關係。 最後，以修正型的Pitzer-Debye-Hückel 模式，來關聯整個實驗數據，獲得不錯的擬合結果。如：溫度在298.15K的KCl電解質水溶液中，個別離子活性係數關聯結果誤差百分率(error ﹪)值皆小於1.5﹪。 This study concerns using ion-selective electrodes to measure the individual ion activity coefficients at different temperature in aqueous solutions of KCl、NaCl、KBr and NaBr. The mean ionic activity coefficients of these electrolytes in aqueous solutions are obtained from the values of the individual ion activity coefficients. The mean ionic activity coefficients of aqueous electrolyte solutions obtained at 298.15 K of present experiments show good agreement to the literature values. The experimental results show that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte. This is due to the ion-ion and ion-solvent interactions, and the nature of its counterion. The ionic activity coefficient the above in electrolytes aqueous solution decreases with increasing temperature at constant concentration. The experimental individual ionic activity coefficients are compared to those obtained from correlation models of chen et al.(1982), Pitzer(1980). Finally, the modified Pitzer-Debye-Hückel model was used to correlate the experimental results with good agreement.
