Why is a neutralization reaction exothermic?
Also, it's important to understand that during an exothermic reaction, bonds are being made and energy is released to the surroundings. This is what ultimately happens during a neutralization reaction that gives its exothermic character.
Take, for instance, the classic reaction between
The complete ionic equation for this reaction is
The net ionic equation is determined by removing the spectator ions (the ions present on both the reactants, and the products' side):
SInce strong acids and strong bases are completely dissociated in solution, no formal bonds are being broken. The formation of two very strong covalent bonds between hydrogen and the hydroxide ion is responsible for the neutralization reaction's exothermic character.
Here's a related question that tackles this process: