Low temperature heat capacity and thermodynamic functions of zirconium (IV) sulfate in the tetrahydrate and anhydrous forms

Abstract

The heat capacities of alpha zirconium (IV) sulfate in its tetrahydrate and anhydrous forms were measured from 1.8 K to 300 K via relaxation calorimetry. The measured heat capacities have been fit to theoretical functions and compared to the available literature. Smoothed entropy and enthalpy increments from 0 K to 300 K were calculated from the fits of the data, and the absolute entropies for Zr(SO₄)₂ ∙ 4.02H₂O and Zr(SO₄)₂ at 298.15 K are 298.80 J∙K⁻¹ mol⁻¹ and 170.57 J∙K⁻¹ mol⁻¹, respectively. The Gibbs energies of formation relative to the elements and to the oxides at 298.15 K were calculated using available enthalpy of formation data. For Zr(SO₄)₂ ∙ 4.02H₂O and Zr(SO₄)₂, respectively, the Gibbs energies of formation at 298.15 K from the elements are −2990.6 kJ∙mol⁻¹ and − 2006.7 kJ∙mol⁻¹ and from the oxides are −270.2 kJ∙mol⁻¹ and − 237.9 kJ∙mol⁻¹.