电位法测定亚磷酸镍溶度积常数探讨

Exploration of measurement of nickel phosphite′s solubility product constant by electric potential method

用电位法测定了亚磷酸镍的溶度积常数logK0.首先设计了一个原电池,由半电池铂金-饱和甘汞电极和半电池镍-亚磷酸镍.亚磷酸根组成,测出了不同亚磷酸根离子活度和不同温度下的原电池电动势,扣除了不同温度下饱和甘汞的电极电势,即得到镍-亚磷酸镍.亚磷酸根的电极电势E.用E值通过Nernst方程式计算出亚磷酸镍的溶解、沉淀过程的活度平衡常数logKa,再用Debye-Hückel方程式将logKa与离子强度联系起来,计算出logKd,用logKd-I作图,外推I趋近于零,求得了不同温度下的一组logK0值,当298 K(25℃)时,logK0=-4.33.再用logK0与热力学温度的倒数(1/T)作图,求得了亚磷酸镍溶解、沉淀过程的ΔH和ΔS,分别为-79.734 kJ.mol-1和184.655 J.mol-1.K-1.

The measurement of nickel phosphite＇s solubility product constant log K0 by electrical potential method is explored. Firstly, a primary cell platinum-saturated calomel electrode, and half-cell was designed, which is composed of a half-cell, nickel-nickel phosphite · phosphite. Different phosphite＇s activity and the primary cell＇s electromotive force under the conditions of different temperatures are measured, and electrode potential （E） of nickel-nickel phosphite · phosphite is obtained by deducting the saturated calomel electrode potential. Then the activity equilibrium constant log K, of nickel phosphite＇s solubilizing and preeipitat via Nernst equation. And then, log K, is connected ing pr with ocess is calculated by means of value E and ionic strength （I） to calculate log Kd by Debye-Hückel equation. A picture of log Kd-I is worked out, a group of values of log K0 are obtained by extrapolating ionic strength （I） to zero. log K0 is -4.33 when the temperature is 298 K （25 ℃）. Aga,n using log K0 and the reciprocal of the thermodynamic temperature（1/T）to work out a picture ,the values of △H and △S in the obtained, which are -- 79. 734 kJ · mol^-1 nickel phosphite＇s solubilizing and precipitating process are 1 and 184. 655 J · mol^-1· K^-1 respectively.