Measurements of Enthalpy Change of Reaction of Formation, Molar Heat Capacity and Constant-Volume Combustion Energy of Solid Complex Yb(Et2dtc)3 (phen)

A ternary solid complex Yb(Et2dtc)3(phen) was obtained from the reaction of hydrous ytterbium chloride with sodium diethyldithiocarbamate (NaEt2dtc), and 1, 10-phenanthroline (o-phen·H2O) in absolute ethanol. The bonding characteristics of the complex were characterized by IR. The result shows Yb3+ bands with two sulfur atoms in the Na(Et2dtc)3 and two nitrogen atoms in the o-phen. The enthalpy change of liquid-phase reaction of formation of the complex ΔrHθm(1), was determined as being (-24.838±0.114) kJ·mol−1 at 298.15 K, by an RD-496 III type heat conduction microcalormeter. The enthalpy change of the solid-phase reaction of formation of the complex ΔrHθm(s), was calculated as being (108.015±0.479) kJ·mol−1 on the basis of an appropriate thermochemistry cycle. The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature during the liquid-phase reaction. Fundamental parameters, the activation enthalpy, ΔHθ≠, the activation entropy, ΔSθ≠, the activation free energy, ΔGθ≠, the apparent reaction rate constant k, the apparent activation energy E, the pre-exponential constant A, and the reaction order n, were obtained by a combination of the reaction thermodynamic and kinetic equations with the data from the thermokinetic experiments. At the same time, the molar heat capacity of the complex cm, p, was determined to be (86.34±1.74) J·mol−1·K−1 by the same microcalormeter. The constant-volume combustion energy of the complex, Δc U, was determined to be (− 17954.08±8.11) kJ·mol−1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHθm, and standard enthalpy of formation, ΔfHθm were calculated to be (-17973.29±8.11) kJ·mol−1 and (-770.36±9.02) kJ·mol−1 respectively.