Since the enthalpy of elements in their natural state is taken to be zero, the heat of formation `(Delta_(f)H)` of compounds

The enthalpies of elements in their standard states are taken as

The enthalpy of elements in their standard states are taken as zero. Hence the enthalpy of formation of a compound is

The heat of formation is the change in enthalpy accompanying the formation of a substance fiom its elements at 298 K and 1 atm pressure. Since the anthalpies of elements are taken to be zero, the heat of formation (triangleH) of compounds

Enthalpies of elements in their standard states are taken as zero. Hence the enthalpy of formation of a compound