Thermodynamic Properties of M2EO4, M2MoxO3x + 1 and Double Chromates (M = Li, Na, K, Rb, Cs; E = Cr, Mo, W)

Resumo

The phase transition temperatures of chromates and molybdates of certain alkali metals, and the melting temperature and enthalpy of polymorphic transformations for tungstates, are determined by means of thermal analysis. Enthalpies of dissolution of rubidium and cesium chromates in water and enthalpies of dissolution of alkali metal tungstates in a melt at 923 K are measured via calorimetry. Standard enthalpies of formation of sought chromates are calculated. The linear correlations between the enthalpies of formation of sulfates, selenates, chromates, tungstates, and molybdates are established, and a linear correlation within − (ΔG^o_ox)^-1-(ΔMV)_ox)⁻¹ coordinates is found for isopolymolybdates.