Standard Gibbs energy of formation of Zn ₁₇Y ₂ and Zn ₁₂Y determined by solution calorimetry and measurement of heat capacity from near zero Kelvin

Abstract

The thermodynamic properties of Zn ₁₇Y ₂ and Zn ₁₂Y were investigated by calorimetry. The standard entropies of formation at 298 K, were determined from measuring the heat capacities, C _p, 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: (Zn ₁₇Y ₂) = – 23.53 ± 1.4 kJ · (mol of atoms) ⁻¹; (Zn ₁₇Y ₂) = – 3.05 ± 0.39 J · K ⁻¹ · (mol of atoms) ⁻¹; (Zn ₁₇Y ₂) = – 22.62 ± 1.4 kJ · (mol of atoms) ⁻¹; (Zn ₁₂Y) = – 23.89 ± 1.8 kJ · (mol of atoms) ⁻¹; (Zn ₁₂Y) = – 0.78 ± 0.41 J · K ⁻¹ · (mol of atoms) ⁻¹; (Zn ₁₂Y) = – 23.66 ± 1.8 kJ · (mol of atoms) ⁻¹. The electronic contribution to the heat capacity of Zn ₁₇Y ₂ and Zn ₁₂Y 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.