Estimation of the standard enthalpy of formation of double oxide

A new estimating method for the standard enthalpy of formation of double oxide at 298.15 K is proposed. The standard enthalpy of formation can be obtained by adding the reaction enthalpy of the simple oxides combining into a double oxide to the sum of the standard enthalpies of formation of the simple oxides. When the reaction enthalpy relates to one mole of two simple oxides combining into a double oxide, the reaction enthalpy (ΔHo) can be predicted from a term, x1x2λ, where x1 and x2 are the mole fractions of the two simple oxides, and λ is a constant. If ΔHo is known for one double oxide, λ can be calculated. Then, ΔHo of other double oxides formed from these two simple oxides can be predicted. If no ΔHo values is known, λ can be estimated from the electronegativities of the component elements.