|
|
|
By definition, chemical
elements in standard states at 298K and 1 atm have zero enthalpy,
|
|
Ho = 0 for each
element in its most stable form at 298K and 1 atm.
|
|
This is an arbitrary
definition, just as defining sea level to be zero altitude.
|
|
|
|
Hence the standard heats of
formation of elements in their most stable forms at 298K an 1 atm is ZERO.
|
|
|
|
Hence the standard enthalpy
of formation of H2(g) is the reaction of H2 (g) -> H2
(g). Which is zero
|
|
|
|
By definition the standard
heat of formation is the heat accompanying the formation of a product from
elements in their standard states.
|
|
|
|
|
|
Hence because of the
definition of the standard heat of formation, the standard heat of formation
of elements in their most stable form at standard conditions is zero.
|
