Thermodynamic equilibrium between melt and crystalline phase of a compoundA(q)B(r) with dystectic melting point - II. Application to the systems KF-K3FMoO4 and KF-K3FWO4

The LeChatelier-Shreder equation, describing the equilibrium between crysta lline phase and melt in the system A-AB when substance AB partially dissoci ates upon melting was applied in the systems KF-K2MoO4 and KF-K2WO4. The di ssociation enthalpy, the heat of fusion at dystectic temperature of fusion, and the degree of dissociation of compounds K3FMoO4 and K3FWO4, 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 t he dissociation degree of K3FMoO4 and K3FWO4 has been found to be alpha (T- fus) = 0.827. Similarly, for the dissociation enthalpy of the reaction AB = A + B the value Delta H-dis(+) = -2462 J mol(-1) was calculated in both sy stems. For the enthalpy of fusion of K3FWO4 the value Delta H-fus(K3FWO4,T- fus) = 59 451 J mol(-1) was calculated. For the enthalpy of fusion of the f ictive nondissociated compounds K3FMoO4 and K3FWO4 the values Delta H-fus(K 3FMoO4,Tfus) = 60 275.8 J mol(-1) and Delta H-fus(K3FWO4,T-fus) = 61 486 J mol(-1) were calculated.