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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 selected as reactants, and sodium hydrate was synthesized by liquid-phase synthesis method. Its composition and structure were characterized by X-ray powder diffraction, chemical and elemental analysis. Calorimeters were used to determine the molar heat capacity of the compound in the temperature range from 78 to 366 K. The experimental data of the molar heat capacity in this temperature region were fitted by the least squares method to obtain the polynomial equation of molar heat capacity (Cp, m) versus temperature (T) , Using this equation for numerical integration, we get the thermal relaxation value every 5K and the thermodynamic function value at 298.15K in this temperature range.In addition, according to Hess’s law, through the design of a reasonable thermochemical cycle, using isothermal environment to dissolve - The reaction calorimeter respectively measured the enthalpies of enthalpy of reaction of the solid phase calorimetric reaction and the product in the selected solvent, so as to determine the reaction enthalpy of reaction: ΔrHm = 29.073 ± 1.05kJ · mol-1. Finally, The standard molar enthalpy of formation for sodium hydrated phthalate was calculated to be -1493.637 ± 1.11 kJ · mol-1 based on the reaction enthalpies and the known thermodynamic data for the other reactants and products.