Rubidium chromate: standard molar enthalpies of solution and formation and the standard molar entropy at 298.15 K, enthalpy increments relative to 298.15 K, the high-temperature heat capacity, and temperatures, enthalpies, and entropies of transition and melting thermodynamic properties of Rb 2CrO 4 from 298.15 to 1500 K

Abstract

Calorimetric measurements are reported on a well-characterized specimen of rubidium chromate Rb 2CrO 4. The standard molar enthalpies of solution and formation at 298.15 K are (25.99±0.06) and −(1410.76±1.90) kJ·mol −1, respectively. The high-temperature enthalpy increments relative to 298.15 K have been determined to 1400 K and the high-temperature heat capacities have been derived from those results. The temperature and enthalpy of the α-to-β transition are 998 K and (5.48±0.50) kJ·mol −1, and the temperature and enthalpy of melting are 1261 K and (31.46±0.80) kJ·mol −1. Based on the solubility, the standard enthalpy of solution, and the estimated activity coefficient, the standard molar entropy S m o(Rb 2CrO 4, 298.15 K) has been estimated as (216±4) J·K −1·mol −1. The thermodynamic properties of Rb 2CrO 4 have been tabulated from 298.15 to 1500 K.