邻苯二甲酸氢铵NH_4(C_8H_5O_4)(s)的低温热容和热化学研究  

Low Temperature Heat Capacities and Thermochemistry of Ammonium Hydrogen Phthalate NH_4(C_8H_5O_4)(s)

作　　者：孔玉霞[1] 邸友莹[1] 龚树文[1] 杨伟伟[1] 孙德志[1] 吕兴强[1] 

机构地区：[1]聊城大学化学化工学院,聊城252059

出　　处：《无机化学学报》2009年第9期1575-1583,共9页Chinese Journal of Inorganic Chemistry

基　　金：国家自然科学基金(No.20673050)资助项目

摘　　要：选择分析纯邻苯二甲酸和浓氨水为反应物,合成了邻苯二甲酸氢铵。利用元素分析、FTIR和X-射线粉末衍射技术表征了它的组成和结构。用精密自动绝热热量计测定了它在78～400K温区的摩尔热容,将该温区的摩尔热容实验值用最小二乘法拟合,得到摩尔热容(Cp,m)随折合温度(X)变化的多项式方程,利用此方程计算出该温区内每隔5K的舒平热容值和相对于298.15K的各种热力学函数值。另外,依据Hess定律,通过设计合理的热化学循环,利用等温环境溶解-反应热量计分别测定所设计反应的反应物和产物在所选溶剂中的溶解焓,得到该反应的反应焓为ΔrHm=(1.787±0.514)kJ·mol-1。最后,利用此反应焓和反应中其他物质的热力学数据计算出邻苯二甲酸氢铵的标准摩尔生成焓为:ΔfHm[NH4(C8H5O4),s]=-(912.953±0.628)kJ·mol-1。Ammonium hydrogen phthalate was synthesized by reaction of phthalic acid with concentrated ammonia water and characterized by Elemental analysis, FTIR and XRD. Low-temperature heat capacities of the title compound NH4（C8H5O4）（S） were measured with a small sample precision automated adiabatic calorimeter over the temperature range of 78 to 400 K. A polynomial equation of heat capacities as a function of the temperature was fitted by least square method. Based on the fitted polynomial, smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at the interval of 5 K. In accordance with Hess law, a reasonable thermochemical cycle was designed, and standard molar enthalpies of dissolution for the reactants and products of the designed reaction in the selected solvent were measured by an isoperibol solution-reaction calorimeter, respectively. In addition, the enthalpy change of the reaction was calculated to be △rHm=（1.787±0.514）kJ·mol^-1 from data of above standard molar enthalpiesof dissolution. Finally, standard molar enthalpy of formation of ammonium hydrogen phthalate was determined to be △f Hm[NH4 （C8 H5O4 ）, s]=-（912.953±0.628） kJ·mol^-1.

关 键 词：邻苯二甲酸氢铵 绝热量热法 低温热容 等温环境溶解-反应量热法 标准摩尔生成焓 

分 类 号：O642[理学—物理化学]