Enthalpy of Formation
ΔHfº
is the standard enthalpy of formation for a compound ... it is the enthalpy
change when a compound is formed from its constituent pure elements
at standard state
(25ºC and 1 atm. For solutions, it's a concentration of 1 M).
Each of the three initial reactions in the Hess' Law example were actually enthalpies of formation, since they represented the formation of the compound from its constituent pure elements:
Each of the three initial reactions in the Hess' Law example were actually enthalpies of formation, since they represented the formation of the compound from its constituent pure elements:
The
enthalpy of formation for a pure element is 0 kJ/mol.
