ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Thermodynamic Equilibrium between Melt and Crystalline Phase of a Compound A_qB_r with Dystectic Melting Point. II. Application to the Systems KF—K₃FMo0₄ and KF—K₃FW0₄

I. Proks, V. Daněk, L. Kosa, and K. Adamkovičová

Institute of Inorganic Chemistry, Slovak Academy of Sciences, SK-842 36 Bratislava

Abstract: The LeChatelier-Shreder equation, describing the equilibrium between crystalline phase and melt in the system A-AB when substance AB partially dissociates upon melting was applied in the systems KF-K₂MoO₄ and KF-K₂WO₄. The dissociation enthalpy, the heat of fusion at dystectic temperature of fusion, and the degree of dissociation of compounds K₃FMo0₄ and K₃FW0₄, formed in the melt, were calculated without using any fictive quantity.Due to the similarity of properties of the systems KF-K₂MoO₄ and KF-K₂WO₄ the dissociation degree of K₃FMo0₄ and K₃FW0₄ has been found to be α(T_fus) = 0.827. Similarly, for the dissociation enthalpy of the reaction AB = A + B the value ∆_dis H₊ = -2462 J mol(-1) was calculated in both systems. For the enthalpy of fusion of K₃FW0₄ the value ∆_fus H (K₃FW0₄,T_fus) = 59 451 J mol^-1 was calculated. For the enthalpy of fusion of the fictive nondissociated compounds K₃FMo0₄ and K₃FW0₄ the values ∆_fusH(K₃FMo0₄,T_fus) = 60 275.8 J mol^-1 and ∆_fusH(K₃FW0₄,T_fus) = 61 486 J mol^-1 were calculated.

Full paper in Portable Document Format: 552a59.pdf

Chemical Papers 55 (2) 59–66 (2001)