ESTIMATION OF THE STANDARD ENTHALPY OF FORMATION OF DOUBLE OXIDE

A new estimating method for the standard enthalpy of formation of doub le oxide at 298.15 K is proposed. The standard enthalpy of formation c an be obtained by adding the reaction enthalpy of the simple oxides co mbining into a double oxide to the sum of the standard enthalpies of f ormation of the simple oxides. When the reaction enthalpy relates to o ne mole of two simple oxides combining into a double oxide, the reacti on enthalpy (Delta H degrees) can be predicted from a term, x(1)x(2) l ambda, where x(1) and x(2) are the mole fractions of the two simple ox ides, and lambda is a constant. If Delta H degrees is known for one do uble oxide, lambda can be calculated. Then, Delta H degrees of other d ouble oxides formed from these two simple oxides can be predicted. If no Delta H degrees values is known, lambda can be estimated from the e lectronegativities of the component elements. (C) 1998 Elsevier Scienc e S.A.