Thermodynamic studies on Rb2CeO3

Rb2CeO3 compound was prepared by conventional solid-state reaction route. The Gibbs energy formation of the compound was determined by measuring the partial pressure of CO2 over the equilibrium phase mixture {Rb2CO3(s) + CeO2(s) + Rb2CeO3(s)} using Knudsen effusion quadrupole mass spectrometry. Gibbs energy formation of the compound, $$\Delta_{\text{f}} G_{\text{m}}^{o}$$ , as a function of temperature is obtained as: $$\Delta_{\text{f}} G_{\text{m}}^{\rm o} \left( {{\text{Rb}}_{2} {\text{CeO}}_{3} ,{\text{s}},T} \right)({\text{kJ}}\;{\text{mol}}^{ - 1} ) \, \left( { \pm 7} \right)\; = \; - 1601 + 0.41 \times \left( {T/K} \right)(991 \le T/K \le 1124)$$ The molar heat capacity of the compound, $$C^{\text o}_{\text{p,m}}$$ , was measured from 390 to 1100 K using a differential scanning calorimeter and is given as: $$C^{\rm o}_{\text{p,m}} \left( {{\text{Rb}}_{2} {\text{CeO}}_{3} ,{\text{s}},T} \right) \, ({\text{J}}\;{\text{mol}}^{ - 1} \;{\text{K}}^{ - 1} ) = 210.8 + 0.0061 \times \left( {T/K} \right){-}6348435/\left( {T/K} \right)^{2}$$ Based on these experimental data, thermodynamic table of the compound was also generated from 298.15 to 1000 K. Standard molar enthalpy of formation $$\Delta_{\text{f}} H_{\text{m}}^{\rm o}$$ (298.15 K) and standard molar entropy $$S_{\text{m}}^{\text o}$$ (298.15 K) of Rb2CeO3 are −1643 kJ mol−1 and 61.5 J K−1 mol−1, respectively.