JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Estimation of the lattice energy and the free energy of formation of the series M4P2O7 (M= Li, Na, K, Rb and Cs)

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Lattice energies and Gibbs energies of formation are determined for a series of alkaline diphosphate (pyrophosphate) of formula M4P2O7(s) where M = Li, Na, K, Rb and Cs. The lattice energy, UPOT, is calculated according to two schema of decomposition using the standard Born-Haber-Fajans (BHF) thermochemical cycle and Glasser equation. The results led to the standard molar enthalpy of formation of potassium diphosphate (K4P2O7) as equals -3212 kJ mol-1. This value differs only by 0.6% from literature data. Free Gibbs energy of formation of these compounds was estimated by the determination of their absolute entropy according to Jenkins and Glasser procedure.

H. Gmati-Ben Khaled, I. Khattech, M. Jemal

Lattice Energy, Enthalpy of formation, Entropy of formation, Gibbs Energy of formation, Alkaline Diphosphate (pyrophosphate)

Pages 208-212

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