Thermodynamics of the coordination compound Zn(Met)(NO3)2•1/2H2O(s) (Met = L-α-methionine) Low temperature heat capacities and the standard molar enthalpy of formation

被引:0
作者
Gao, Sheng-Li [1 ]
机构
[1] Baoji Univ Arts & Sci, Dept Chem & Chem Engn, Baoji 721013, Peoples R China
基金
中国国家自然科学基金;
关键词
Adiabatic calorimetry; Heat capacity; Standard molar enthalpy of formation; Amino acids; Isoperibol solution-reaction calorimetry; AMINO-ACIDS; ZINC-SULFATE; CALORIMETER;
D O I
10.1007/s10973-011-1828-7
中图分类号
O414.1 [热力学];
学科分类号
摘要
Low temperature heat capacities of the solid coordination compound, Zn(Met)(NO3)(2)center dot 1/2H(2)O(s), have been measured by a precision automated adiabatic calorimeter over the temperature range 78-371 K. The initial dehydration temperature of the coordination compound is determined to be, T-D = 325.05 K, by analysis of the heat-capacity curve. The experimental values of molar heat capacities in the temperature region have been fitted to a polynomial equation of heat capacities with the reduced temperature (X), [X = f(T)], by a least squares method. Smoothed heat capacities and thermodynamic functions relative to the standard reference temperature 298.15 K of the compound are derived from the fitted polynomial equation and listed at 5 K internals. Enthalpies of dissolution of {ZnSO4 center dot 7H(2)O(s) + 2NaNO(3)(s) + L-Met (s)} and {Zn(Met)(NO3)(2)center dot 1/2H(2)O(s) + Na2SO4(s)} in 100 cm(3) of 2 mol dm(-3) HCl(aq) at T = 298.15 K have been determined to be Delta H-d(m,1)0 = (56.929 +/- 0.051) kJ mol(-1) and Delta H-d(m,2)0 = (37.337 +/- 0.029) kJ mol(-1), respectively, with an isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the compound is determined to be Delta H-f(m)0 [Zn(Met)(NO3)(2)center dot 1/2H(2)O, s] = -(1327.08 +/- 0.75) kJ mol(-1) from the enthalpies of dissolution of the reactants and products and other thermodynamic data by a Hess' thermochemical cycle.
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页码:937 / 943
页数:7
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