why can enthalpy change be measured but not enthalpy. surley to calculate change in enthalpy you need to know the enthalpy before and enthalpy after
Chemical potential energy is like gravitational potential energy, in that you cannot put an absolute value on it.
The gravitational potental energy is a consequence of a mass's position in the universe relative to absolutely every other mass.
The chemical potential energy is a function of a substances atoms' position in the universe relative to absolutely every other atom.