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human
ELI5: Why is Neutralization an Exothermic Reaction?

From what I know and read, bonding atoms release energy in the form of heat. Can someone explain it in details? Using HCl + NaOH reaction as an example will be helpful as well.

\-Thanks in Advance!
gpt
First let's keep in mind that the rule is as follows:

Breaking a given bond is always endothermic

Forming a given bond is always exothermic

When we talk about whether a ***reaction*** is exothermic or endothermic, we are talking about the summation of the individuals bonds broken and formed and the net energy release or absorbed.

 For example, dissociating Na from OH is endothermic. Same for H and Cl. But the bonding of Na and Cl, and that of H and OH, is exothermic. To know whether the neutralization reaction releases or absorbs energy, you need to know whether the energy needed for the endothermic part is less or more than the energy released by the exothermic part.

If you look at how much energy it takes to break Na from OH and H from Cl, then how much energy you get for bonding Na and Cl and bonding H and OH (you can do that by looking at heat of formation tables and such), you sum those and realize you at the end of the reaction, there is net release of energy, which is why it's exothermic.