Abstract
Three independent studies have been reported on the free energy of formation of NiWO4. Results of these measurements are analyzed by the “third-law” method, using thermal functions for NiWO4 derived from both low and high temperature heat capacity measurements. Values for the standard molar enthalpy of formation of NiWO4 at 298·15 K obtained from “third-law” analysis are compared with direct calorimetric determinations. Only one set of free energy measurements is found to be compatible with calorimetric enthalpies of formation. The selected value for Δf H 0m (NiWO4, cr, 298·15 K) is the average of the three calorimetric measurements, using both high temperature solution and combustion techniques, and the compatible free energy determination. A new set of evaluated data for NiWO4 is presented.
Abbreviations
- C 0p,m :
-
Standard molar heat capacity
- T :
-
Thermodynamic temperature in kelvin
- Δf G 0m :
-
Standard molar Gibbs free energy of formation from elements
- Δi G 0m :
-
Standard molar Gibbs free energy change for reaction i
- Δf H 0m :
-
Standard molar enthalpy of formation from elements
- cr:
-
crystal
- GEF:
-
Gibbs energy function
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Raj, P.M. A critical assessment of the standard molar gibbs free energy of formation of NiWO4 . Bull. Mater. Sci. 18, 623–630 (1995). https://doi.org/10.1007/BF02744848
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DOI: https://doi.org/10.1007/BF02744848