Title of article :
Formation Gibbs energy of K2NbF7, K2NbOF5, and K2NbO2F3 from electrochemical measurements
Author/Authors :
V Van، نويسنده , , V Dan?k، نويسنده ,
Issue Information :
دوهفته نامه با شماره پیاپی سال 2001
Abstract :
The formation Gibbs energies of molten K2NbF7, K2NbOF5, and K2NbO2F3 at the temperature of 750°C were calculated from the previously performed voltammetric and chronopotentiometric measurements in the system LiF–NaF–K2NbF7–Na2O and from the equilibrium constants of reactions leading to the formation in the melts of the individual oxyfluoroniobates.
For the formation Gibbs energy of K2NbF7 the average value ΔfG0(K2NbF7)=−(1340±25) kJ mol−1 was obtained. For K2NbOF5 the formation Gibbs energy is ΔfG0(K2NbOF5)=−(1526±16) kJ mol−1. This value may, however, not be exactly correct since the product of the electrochemical reduction was not pure niobium, but the solid solution of oxygen in niobium. For the formation Gibbs energy of K2NbO2F3 the value ΔfG0(K2NbO2F3)=−(1100±100) kJ mol−1 was calculated. This value may be charged by a substantial error as well due to the probably incorrect value of the formation Gibbs energy of K2NbOF5.
Keywords :
Electrochemistry , Oxofluoroniobates , Gibbs energy
Journal title :
Thermochimica Acta
Journal title :
Thermochimica Acta