Low-temperature heat capacity and standard molar enthalpy of formation of the complex Zn(Thr)SO4 center dot H2O(S)

摘要

Low-temperature heat capacities of the complex Zn(Thr)SO4.H2O (s) have been precisely measured with a small sample adiabatic calorimeter over the temperature range from 78 to 373 K. The initial dehydration temperature of the complex (T-d = 325.50 K) has been obtained by analysis of the heat-capacity curve. The experimental values of molar heat capacities have been fitted to a polynomial equation by least square method. The standard molar enthalpy of formation of the complex has been determined from the enthalpies of dissolution (Delta(d)H(m)(Theta)) of [ZnSO4.7H(2)O(S)+Thr (s)] and Zn(Thr)SO4.H2O (s) in 100 ml of 2 mol dm(-3) HCl solvent as: Delta(f)H(m,Zn(Thr)SO4.H2O)(Theta) = -2111.7 +/- 3.4 kJ mol(-1). These experiments were made by using an isoperibol solution calorimeter at 298.15 K. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 14]