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Enthalpy of Formation

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.

CaHbOcNdSeFfClgBrhIiaC(graphite) + 0.5bH2(g) + 0.5cO2(g) + 0.5dN2(g) + 0.5eS(II) + 0.5fF2(g) + 0.5gCl2(g) + 0.5hBr2(l) + 0.5iI2(c)

Enthalpy of Formation Δhf° 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.

The enthalpy of formation in the condensed states (crystal & liquid) are typically evaluated from enthalpies of combustion determined by combustion-bomb calorimetry. See Cox and Pilcher, 1970 [42] 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. These values are are taken from the following literature sources:
Compound State Citation
CO2 g [43]
H2O l [43]
HF aq [44]
HCl aq [45]
HBr aq [45]
H2SO4 aq [45]

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