Standard Gibbs energy of formation of Zn17Y2 and Zn12Y determined by solution calorimetry and measurement of heat capacity from near zero Kelvin

Abstract

Abstract The thermodynamic properties of Zn17Y2 and Zn12Y were investigated by calorimetry. The standard entropies of formation at 298 K, were determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpies of formation at 298 K, were determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energies of formation at 298 K, were determined from these data. The results obtained are: (Zn17Y2) = – 23.53 ± 1.4 kJ · (mol of atoms)−1; (Zn17Y2) = – 3.05 ± 0.39 J · K−1 · (mol of atoms)−1; (Zn17Y2) = – 22.62 ± 1.4 kJ · (mol of atoms)−1; (Zn12Y) = – 23.89 ± 1.8 kJ · (mol of atoms)−1; (Zn12Y) = – 0.78 ± 0.41 J · K−1 · (mol of atoms)−1; (Zn12Y) = – 23.66 ± 1.8 kJ · (mol of atoms)−1. The electronic contribution to the heat capacity of Zn17Y2 and Zn12Y is found to be similar to pure zinc, indicating that the valence electrons of yttrium in the compound are trapped by the density of states for zinc.