CONTROVERSY ON THE FREE-ENERGY OF FORMATION OF CAO-ADDITIONAL EVIDENCE IN SUPPORT OF THERMOCHEMICAL DATA

Citation
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
ISSN journal
10735615
Volume
27
Issue
4
Year of publication
1996
Pages
647 - 651
Database
ISI
SICI code
1073-5615(1996)27:4<647:COTFOF>2.0.ZU;2-S
Abstract
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.