My concept of enthalpy change is that the change is based on limits that approach zero. Something like the heat evolved/absorbed per second (but instead of second its a infinitely small). A+B→C ΔH=100J/mole of A (standard enthalpy change) And as such when the reaction first proceeds the initial ΔH is the enthalpy change of reaction for the reactants undergoing reaction(100J/mole of A reacted). However, at the next instance some product is formed and as such some of the backwards reaction would occur and so there is a negative enthalpy change (-100J/mole of A formed). And the backwards reaction keeps increasing until the forward reaction = backwards reaction and so the ΔH drops to zero. Is this concept right? If so how do we determine the total energy released in that reaction?