Metallurgical and Materials Transactions B

, Volume 27, Issue 4, pp 647–651

Controversy on the free energy of formation of CaO—Additional evidence in support of thermochemical data

  • K. T. Jacob
  • Viji Varghese
Physical Chemistry

DOI: 10.1007/BF02915662

Cite this article as:
Jacob, K.T. & Varghese, V. Metall and Materi Trans B (1996) 27: 647. doi:10.1007/BF02915662


The standard free energies of formation of CaO derived from a variety of high-temperature equilibrium measurements made by seven groups of experimentalists are significantly different from those given in the standard compilations of thermodynamic data. Indirect support for the validity 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:
$$\begin{gathered} CaO + MgF_2 \to MgO + CaF_2 \hfill \\ \Delta G^ \circ = - 68,050 - 2.47 T( \pm 100) J mol^{ - 1} \hfill \\ SrO + CaF_2 \to SrF_2 + CaO \hfill \\ \Delta G^ \circ = - 35,010 + 6.39 T( \pm 80) J mol^{ - 1} \hfill \\ \end{gathered} $$
The standard free energy changes associated with cell reactions agree with data in standard compilations within ±4 kJ mol−1. The results of this study do not support recent suggestions for a major revision in thermodynamic data for CaO.

Copyright information

© The Minerals, Metals & Materials Society - ASM International - The Materials Information Society 1996

Authors and Affiliations

  • K. T. Jacob
    • 1
  • Viji Varghese
    • 1
  1. 1.Indian Institute of ScienceBangaloreIndia