摘要
选择邻苯二甲酸和氢氧化钠作为反应物,利用液相合成方法合成了水合邻苯二甲酸钠.利用X射线粉末衍射、化学与元素分析等方法表征了它的组成和结构.利用精密自动绝热热量计测定了该化合物在78～366K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)对温度(T)的多项式方程,用此方程进行数值积分得到此温度区间内每隔5K的舒平热容值和相对于298.15K时的热力学函数值.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-反应热量计分别测量了固相量热反应的反应物和产物在所选溶剂中的溶解焓,从而确定反应的反应焓为:ΔrHm=29.073±1.05kJ·mol-1.最后,利用反应的反应焓和其它反应物和产物已知的热力学数据计算出水合邻苯二甲酸钠的标准摩尔生成焓为:-1493.637±1.11kJ·mol-1.
Phthalic acid and sodium hydroxide were chosen as the reactants and a product of hydrated sodium phthalate was synthesized by the method of liquid phase synthesis. An X-ray powder diffraction technique,chemical and elemental analyses were applied to characterize the composition and structure of the compound. Low-temperature heat capacities of the substance were measured by a precision automated adiabatic calorimeter over a temperature range from 78 to 366 K. A polynomial equation of the heat capacities as a function of the temperature was fitted by the least-squares method. Based on the fitted polynomial,the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated at an interval of 5 K. A reasonable thermochemical cycle was designed on the basis of the Hess law,and the standard molar enthalpies of dissolution for the reactants and products of the designed solid phase reaction in the selected solvents were measured by an isoperibol solution-reaction calorimeter,respectively. In addition,the enthalpy change of the reaction was determined to be Δ r Hm= 29.073±1.05 kJ·mol-1 from the data of the above standard molar enthalpies of dissolution. Eventually,the standard molar enthalpy of formation of hydrated sodium phthalate was derived to be -1493.637 ±1.11 kJ·mol-1 by the combination of the enthalpy change of the reaction with other auxiliary thermodynamic quantities.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2010年第4期294-300,共7页
Acta Chimica Sinica
基金
国家自然科学基金(No.20673050
20973089)资助项目
关键词
水合邻苯二甲酸钠
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
hydrated sodium phthalate
adiabatic calorimetry
low-temperature heat capacity
isoperibol solution-reaction calorimetry
standard molar enthalpy of formation
