Which reaction is exothermic

A reaction is exothermic when it releases energy during a chemical reaction.

An exothermic reaction is a chemical reaction that releases energy by light or heat. It is the opposite of an endothermic reaction. The opposite of an exothermic process is an endothermic process, one that absorbs energy in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions, where as in chemical bond energy that will be converted to thermal energy (heat).