Formation Reactions
The formation reaction is defined as formation of the specified compound from its constituent elements in their standard states. A generalized reaction can be written for all possible formation reactions that can be evaluated with
TDE.
a C(graphite) + (1/2)b H2(gas) + (1/2)c O2(gas) + (1/2)d N2(gas) + e S(standard state) +
(1/2)f F2(gas) + (1/2)g Cl2(gas) + (1/2)h Br2(standard state) + (1/2)i I2(standard state) = CaHbOcNdSeFfClgBrhIi
Enthalpy of Formation for the stable phase at T = 298.15 K
The enthalpy of formation for the stable phase at
T = 298.15 K (
p = 101.325 kPa) is evaluated as a pure-compound property. See
Pure Compound Evaluation.
The enthalpy of formation in the condensed states (crystal & liquid) are typically evaluated from enthalpies of combustion determined by combustion-bomb calorimetry. (See reference 15 for details of this method.)
Conversion of enthalpies of combustion to enthalpies of formation requires use of some Key Values, such as the enthalpy of formation at T = 298.15 K and p = 101.325 kPa for water and carbon dioxide.
Formation Properties (Enthalpy, Entropy, Gibbs Energy) as a function of temperature
The enthalpies of formation for all phases possible as a function of temperature (with
p = 101.325 kPa) are evaluated through the
Reaction Property Evaluation sequence.