Low-Temperature Heat Capacities and Thermodynamic Properties of Triaquabenzoatocalcium Monobenzoate [Ca(Ben)(H₂O)₃](Ben)(s) (Ben = Benzoate)

Abstract

Triaquabenzoatocalcium monobenzoate [Ca(Ben)(H 2 O) 3 ](Ben)(s) was synthesized by the method of liquid phase reaction. Chemical and element analyses and X-ray crystallography were used to characterize the composition and structure of the complex. The lattice potential energy of the compound was calculated to be U POT ) 426.61 kJ · mol -1 on the basis of crystal structure information. Low-temperature heat capacities over the temperature range from (78 to 360) K were measured by an automated adiabatic calorimeter, and a polynomial equation was fitted by the least-squares method. On the basis of 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 intervals of 5 K. The thermal decomposition of the complex was studied using TG and DSC analyses. In accordance with Hess's law, a reasonable thermochemical cycle was designed based on the preparation reaction of the compound. The standard molar enthalpies of dissolution for the reactants and product of the reaction in the selected solvent were measured by an isoperibol solutionreaction calorimeter. The enthalpy change of the liquid phase reaction was calculated to be ∆ r H m o ) -(46.68 ( 0.40) kJ · mol -1 , and the standard molar enthalpy of formation of the complex was determined to be ∆ f H m o [Ca(Ben)(H 2 O) 3 ](Ben),s ) -(2088.2 ( 1.1) kJ · mol -1 by means of the enthalpy change of the reaction and other auxiliary thermodynamic quantities.

Low-temperature heat capacities and standard molar enthalpy of formation of 2-pyrazinecarboxylate cupric(II) complex Cu(pyza)2(H2O)2

“…The principle and structure of the calorimeter were described in detail elsewhere [9,12]. The reliability of the calorimeter was verified previously by measuring dissolution enthalpy of KCl (calorimetrically primary standard) in double-distilled water at T = 298.15 K. Relative deviation of the experimental result compared with corresponding published standard data was within ±0.30 % [13].…”

“…Kong et al College of Chemistry and Chemical Engineering, Liaocheng University, China. The principle and structure of the adiabatic calorimeter were described in detail elsewhere [9,10]. Briefly, the calorimeter mainly comprised a sample cell, a platinum resistance thermometer, an electric heater, inner, middle, and outer adiabatic shields, three sets of sixjunction chromel-constantan thermopiles installed between the calorimetric cell and the inner shield, between the inner and middle shields, and between the middle and outer shields, respectively, and a high-vacuum can.…”

“…1,-z temperature drift rates of the sample cell measured in an equilibrium period were always kept within (10 -3 -10 -4 ) K min -1 during the acquisition of all heat capacity data. The data of heat capacities and corresponding equilibrium temperature have been corrected for heat exchange of the sample cell with its surroundings [9]. The sample mass used for calorimetric measurements was 2.1230 g, which was equivalent to 6.140 9 10 -3 mol in terms of its molar mass, M = 345.76 g mol -1 .…”

Crystal structure and thermochemical properties of n-decylammonium ethyl sulfate (C10H21NH3SO4C2H5)(s)

“…The precisions of the temperature controlling of the thermostat and temperature measuring of calorimetric vessel are determined to be ±0.001 K and ±0.0001 K, respectively. The principle and structure of the calorimeter are described in detail elsewhere [8].…”

Low-Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Ethylenediammonium Tetrachlorocobaltate(II) Chloride (H3NCH2CH2NH3)2[CoCl4]Cl2(s)

“…The principle and structure of the calorimeter have been described in detail elsewhere. 7 The thermistor was adopted as the sensor for controlling temperature in the thermostatic bath. However, the input signal of the modified high-precision temperature controller (model: DWT-702, manufactured by Shanghai No.…”