硼砂水溶液的低温热容及热化学性质研究  

Low-Temperature Heat Capacities and Thermodynamic Properties of Aqueous Na_2B_4O_7 Solution

作　　者：孟庆芬[1] 谭志诚[2] 董亚萍[1] 冯海涛[1] 李武[1] 

机构地区：[1]中国科学院青海盐湖研究所,西宁810008 [2]中国科学院大连化学物理研究所,中国离子液体实验室和热化学实验室,大连116023

出　　处：《无机化学学报》2010年第8期1333-1338,共6页Chinese Journal of Inorganic Chemistry

基　　金：国家"十一五"科技支撑计划(No.2006BAB09B07);2007年西部之光联合学者项目资助

摘　　要：利用精密绝热量热仪测定了0.03355mol·kg-1的硼砂水溶液在78～351K温区的热容,从实验热容测定结果得到了该水溶液的凝固点为272.905K。用最小二乘法将实验热容值对温度进行拟合,建立了该溶液的热容随温度变化的多项式方程。根据热力学函数关系式,用此多项式方程进行数值积分,获得了以298.15K为基准的该溶液在80～350K温区每隔5K的热力学函数值,并计算出摩尔熔化焓和熔化熵分别为4.536kJ·mol-1和16.22J·K-1·mol-1。根据溶液凝固点降低值,计算出了该溶液的活度为0.99763。The molar heat capacities of aqueous Na2B4O7 solution with concentration of 0.033 55 mol·kg-1 were measured by a precision automated adiabatic calorimeter in the temperature range from 78 K to 351 K. The fusion transition at T =272.905 K was observed from the heat capacity measurements. According to the polynomial equations of heat capacity as a function of temperature and thermodynamic relationship,the thermodynamic functions （HT-H298.15K） and （ST-S298.15K） of the aqueous borax decahydrate solution were derived in the temperature range from about 80 to 350 K with an interval of 5 K. The molar enthalpy and entropy of the phase transition were determined to be 4.536 kJ·mol^-1 and 16.62 J·K-1·mol^-1. The activity of the solution was determined to be 0.997 63 by using the freezing point depression of the solution based on the liquid-solid phase equilibrium rule.

关 键 词：硼砂水溶液 低温热容 热力学函数 绝热量热 

分 类 号：O613.81[理学—无机化学] O642.3[理学—化学]