#dilution is a process in which the concentration of hydrogen ions is decreases in per unit volume . It is a highly exothermic reaction. Sulphuric acid ( H 2 SO 4 ) is one of the most concentrated acids. When it is diluted with water, the reaction occurs very quickly thereby water is protonated releasing more energy in the form of heat.
Dilution of sulfuric acid: In this reaction, acid is added to water to form a dilute solution of dilute sulfuric acid. Because of the formation of hydrogen bonds with water, energy is released by molecules and later, the water absorbs the same energy. So, this reaction is an exothermic one. Very slowly add the concentrated acid to the water with constant stirring. It is important to stir whilst adding the acid to the water to avoid a layer of concentrated acid forming at the bottom of the beaker creating a temperature gradient. While diluting, the #concentrated sulphuric acid should be added to water because acid being heavier, it settles down and the evolved heat is dissipated in the water itself, and hence the spurting of #acid. The water on coming in contact with acid suddenly changes to steam by the heat produced during the reaction.