High-temperature heat capacity measurements were obtained for Cr2O3, FeCr2O4, ZnCr2O4, and CoCr2O4 using a differential scanning calorimeter. These data were combined with previously available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier Kelley Cp(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier Kelley equations in combination with recent S (298) evaluations. Finally, a database of high-temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs free energies of Cr2O3, FeCr2O4, and CoCr2O4 were referenced by averaging the most reliable results at reference temperatures of (1100, 1400, and 1373) K, respectively, while Gibbs free energies for ZnCr2O4 were referenced to the results of Jacob [K.T. Jacob, Thermochim. Acta 15 (1976) 79 87] at T = 1100 K. Thermodynamic extrapolations from the high-temperature reference points to T = 298.15 K by application of the heat capacity correlations gave DfG (298) = ( 1049.96, 1339.40, 1428.35, and 1326.75) kJ Ae mol 1 for Cr2O3, FeCr2O4, ZnCr2O4, and CoCr2O4, respectively.
Compounds
#
Formula
Name
1
Cr2O3
chromic oxide
2
Cr2FeO4
iron(II) chromium(III) tetraoxide
3
Cr2O4Zn
zinc(II) chromium(III) oxide
4
CoCr2O4
dichromium(III) cobalt(II) oxide
Datasets
The table above is generated from the ThermoML associated json file (link above).
POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied;
the numbers refer to the table of compounds on the left.
Type
Compound-#
Property
Variable
Constraint
Phase
Method
#Points
POMD
1
Molar heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Large sample (1 g) DSC
98
POMD
2
Molar heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Large sample (1 g) DSC
128
POMD
3
Molar heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Large sample (1 g) DSC
142
POMD
4
Molar heat capacity at constant pressure, J/K/mol ; Crystal