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

Calorimetric measurements are reported on a well-characterized specimen of rubidium chromate Rb2CrO4. 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 S0sub(m)(Rb2CrO4, 298.15 K) has been estimated as (216 +- 4) J.K-1.mol-1. The thermodynamic properties of Rb2CrO4 have been tabulated from 298.15 to 1500 K. (author)