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
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.