Thermodynamic Investigation of Electrolytes of the Vanadium Redox Flow Battery (V): Conductivity and Ionic Dissociation of Vanadyl Sulfate in Aqueous Solution in the 278.15–318.15 K Temperature Range
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Precise measurements of electrical conductivities of aqueous VOSO4 solutions at various molalities were performed from 278.15 to 318.15 K in 5 K intervals. In terms of Fuoss’s equation and Shedlovsky’s equation, the limiting molar conductance, Λ 0, and the dissociation constant, K d, of the ion-pair [VOSO4]0 were determined. From an empirical equation for the temperature dependence of dissociation constants, the thermodynamic functions for the dissociation process of the ion-pair [VOSO4]0 were calculated. It is discovered that the reaction for ion-pair dissociation is unfavorable under normal pressure and room temperature because the standard state dissociation Gibbs energy (ΔG 0) > 0. The calculated values of the dissociation entropy and the dissociation enthalpy are negative, indicating that the dissociation entropy opposes the dissociation process.
KeywordsVanadium redox flow battery Ion pair Dissociation constant Conductivity Dissociation entropy Vanadyl sulfate
This research was supported by the National Nature Science Foundation of China (General Programs Numbers 21373009 and 21573257).
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