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选择分析纯烟酸和一水氢氧化锂为反应物,利用水热合成方法合成了无水烟酸锂.利用FTIR和X射线粉末衍射等方法表征了它的结构.用精密自动绝热热量计测定了它在78～400K温区的低温热容,将该温区的摩尔热容实验值用最小二乘法拟合,得到热容随温度变化的多项式方程.用此方程进行数值积分,得到温区内每隔5K的舒平热容值和相对于298.15K时的各种热力学函数值.在此基础上,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该反应的反应物和生成物在所选溶剂中的溶解焓,从而得到此反应的反应焓为:ΔrHm=-(20.21±0.41)kJ·mol-1.最后,依据Hess定律计算出无水烟酸锂的标准摩尔生成焓为:ΔfHm[Li(C6H4NO2),s]=-(278.29±1.01)kJ·mol-1.
Hydrotalcite-free lithium nickelate was synthesized by the hydrothermal synthesis method using pure nicotinic acid and lithium hydroxide monohydrate as reactants, and its structure was characterized by FTIR and X-ray powder diffractometry.It was determined by means of a precision automatic adiabatic calorimeter It is the low temperature heat capacity in the temperature range of 78 ~ 400K, and the experimental value of the molar heat capacity in this temperature zone is fitted by the least squares method to get the polynomial equation of the heat capacity with temperature. Using this equation for numerical integration, Every 5K of the heat capacity and the value of thermodynamic function at 298.15 K. On this basis, by designing a reasonable thermochemical cycle, using the isothermal environment dissolved-reaction calorimeter to measure the reactants And the enthalpy of formation of the product in the solvent of choice, the enthalpy of reaction is: ΔrHm = - (20.21 ± 0.41) kJ · mol-1. Finally, according to Hess’s law, calculate the standard mole of anhydrous lithium nicotinate The enthalpy of formation is: ΔfHm [Li (C6H4NO2), s] = - (278.29 ± 1.01) kJ · mol-1.