Endothermic Reaction and Exothermic Reaction

Exothermic reaction is a reaction that releases or remove heat, flowing from system to environment.

∆H reaction = H product - H reagent
                    = small - large 
                    = negative 

Reaction A+B --> C ; ∆H = - x kal

Endothermic reaction is a reaction that absorbs heat, flowing from the environment to the system.

∆H reaction = H product - H reagent 
                    = large – small

                    = positive 

Reaction P+Q --> R ; ∆H = +y kal

Graphics Endothermic Reaction and Exothermic Reaction