Thermodynamic studies on Pr2TeO6

The standard Gibbs energy of formation of Pr₂TeO₆ $ (Updelta_{text{f}} G^{^circ } left( {{ Pr }_{ 2} {text{TeO}}_{ 6} ,;{text{s}}} right)) $ was derived from its vapour pressure in the temperature range of 1,400–1,480 K. The vapour pressure of TeO₂ (g) was measured by employing a thermogravimetry-based transpiration method. The temperature dependence of the vapour pressure of TeO₂ over the mixture Pr₂TeO₆ (s) + Pr₂O₃ (s) generated by the incongruent vapourization reaction, Pr₂TeO₆ (s) = Pr₂O₃ (s) + TeO₂ (g) + ½ O₂ (g) could be represented as: $ { log }left{ {{{pleft( {{text{TeO}}_{ 2} ,;{text{g}}} right)} mathord{left/ {vphantom {{pleft( {{text{TeO}}_{ 2} ,;{text{g}}} right)} {{text{Pa}} pm 0.0 4}}} right. kern-0em} {{text{Pa}} pm 0.0 4}}} right} = 19. 12- 27132; left({rm{{{text{K}}}}/T} right) $ . The $ Updelta_{text{f}} G^{^circ } ;left( {{ Pr }_{ 2} {text{TeO}}_{ 6} } right) $ could be represented by the relation $ left{ {{{Updelta_{text{f}} G^{^circ } left( {{ Pr }_{ 2} {text{TeO}}_{ 6} ,;{text{s}}} right)} mathord{left/ {vphantom {{Updelta_{text{f}} G^{^circ } left( {{ Pr }_{ 2} {text{TeO}}_{ 6} ,;{text{s}}} right)} {left( {{text{kJ}},{text{mol}}^{ - 1} } right)}}} right. kern-0em} {left( {{text{kJ}},{text{mol}}^{ - 1} } right)}} pm 5.0} right} = - 2 4 1 5. 1+ 0. 5 7 9 3;left(T/{text{K}}right) .$ Enthalpy increments of Pr₂TeO₆ were measured by drop calorimetry in the temperature range of 573–1,273 K and heat capacity, entropy and Gibbs energy functions were derived. The $ Updelta_{text{f}} H_{{298;{text{K}}}}^{^circ } ;left( {{ Pr }_{ 2} {text{TeO}}_{ 6} } right) $ was found to be $ {{ - 2, 40 7. 8 pm 2.0} mathord{left/ {vphantom {{ - 2, 40 7. 8 pm 2.0} {left( {{text{kJ}},{text{mol}}^{ - 1} } right)}}} right. kern-0em} {left( {{text{kJ}},{text{mol}}^{ - 1} } right)}} $ .