Kt. Jacob et V. Varghese, CONTROVERSY ON THE FREE-ENERGY OF FORMATION OF CAO-ADDITIONAL EVIDENCE IN SUPPORT OF THERMOCHEMICAL DATA, Metallurgical and materials transactions. B, Process metallurgy and materials processing science, 27(4), 1996, pp. 647-651
Citations number
27
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
The standard free energies of formation of CaO derived from a variety
of high-temperature equilibrium measurements made by seven groups of e
xperimentalists are significantly different from those given in the st
andard compilations of thermodynamic data. Indirect support for the va
lidity of the compiled data comes from new solid-state electrochemical
measurements using single-crystal CaF2 and SrF2 as electrolytes. The
change in free energy for the following reactions are obtained: CaO MgF2 --> MgO + CaF2 Delta G degrees = -68,050 -2.47 T(+/-100) J mol(-1
) SrO + CaF2 --> SrF2 + CaO Delta G degrees = -35,010 + 6.39 T (+/-80)
J mol(-1) The standard free energy changes associated with cell react
ions agree with data in standard compilations within +/- 4 kJ mol(-1).
The results of this study do not support recent suggestions for a maj
or revision in thermodynamic data for CaO.