I have been reading about endothermic and exothermic reactions, as well as change in enthalpy.

From what I have read, an exothermic reaction is where more energy is given out as bonds are made when products form than energy taken in as the bonds of reactants are broken.

Wouldn't this mean that the products have more enthalpy? However, a diagram online shows this (https://www.bbc.com/bitesize/guides/zg84y4j/revision/2):

enter image description here

Why does this diagram show that more energy is taken in as the bonds of reactants are broken? Isn't it incorrect?

I am only just getting started with this topic so I'm just learning concepts. I am not yet familiar with the formulas.

  • $\begingroup$ Is the energy level of reactants and products that counts. The diagram is clear and energy release is schematically shown by the green arrow. The products are more stable. They have more energy in the sense that you would have to input it to the system in order to reverse the reaction. Look at it with an analogy of a mass at different eight. But I am not sure what you are asking for, the question isn't that clear $\endgroup$
    – Alchimista
    Dec 21, 2018 at 10:44

1 Answer 1


Wouldn't this mean that the products have more enthalpy?

The products have less enthalpy, maybe the following diagram remediates misconception : enter image description here

$ΔH=Σproducts-Σreactants = {-965.5 -(-74.87)}=-890.63$

  • $\begingroup$ Is the energy of reactants and products in the ground state of all states (vibration, rotational, electronic)? $\endgroup$
    – ado sar
    May 5, 2020 at 12:13

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