Question

why should not add water to concentrated acid?

Answer 1

because when we add water in concentrated acid heat and energy is prouduced .so if we want to dilute the acid we add very small amount of water slowly slowly . but if we add a large amount of water quickly in the acid it can be dangerous because of explosion.

Answer 2

So much heat is released that the solution may boil very violently, splashing concentrated acid out of the container! If you add acid to water, the solution that forms is very dilute and the small amount of heat released is not enough to vaporize and spatter it. So Always Add Acid to water, and never the reverse.