原电池电动势法测定热力学函数实验改进

Improvement on the Experiment of Measuring the Thermodynamic Function by the Electromotive Force Method

常规电动势法测定热力学函数存在电动势的温度系数不稳定,仍至无法估计或修正等问题。使用改进型盐桥,在20~50°C温度范围内,对比测定了两支参比电极(氯化银和甘汞电极)组成的原电池的电动势。结果表明,其温度系数为正(2.22×10^(-4)V℃^(-1)),反应的热力学函数变化值Δ_rG_m(298 K)、Δ_rS_m(298 K)和Δ_rH_m(298K)分别为-52.87 k J·mol^(-1)、-67.14 J·K^(-1)·mol^(-1)、-69.98 k J·mol^(-1)。与热力学函数理论值相比,其相对误差分别为3.7%、-2.4%和-2.5%。满足基础物理化学实验教学要求。

Aiming at the problem that the temperature coefficient of electromotive force is not stable and can not be estimated or modified in measuring the thermodynamic function by the conventional electromotive force method, improved salt bridges were used to determine the electromotive force of the primary battery composed of silver chloride reference electrode and calomel electrode at 20~50°C. The results show that the temperature coefficient is positive（2.22×10^-4V·°C^-1）, thermodynamic function change values of the reaction ΔrGm（298 K）, ΔrSm（298 K） and ΔrHm（298 K） are-52.87 k J·mol^-1,-67.14 J·K^-1 mol^-1,-69.98 k J·mol^-1, respectively. Compared with the theoretical values, the relative errors are 3.7%,-2.4% and -2.5%, respectively.