1. The reaction of acid and water is an exothermic reaction.
2. When concentrated acid is added to water for preparing dilute acid, then heat is evolved gradually and easily absorbed by the large amount of water.
3. If water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and
cause acid burns. Even the glass container may break due to excessive heating.
4. So, the dilution of a concentrated acid should always be done by adding concentrated acid to water and not by adding water to acid.
2. When concentrated acid is added to water for preparing dilute acid, then heat is evolved gradually and easily absorbed by the large amount of water.
3. If water is added to concentrated acid to dilute it, then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and
cause acid burns. Even the glass container may break due to excessive heating.
4. So, the dilution of a concentrated acid should always be done by adding concentrated acid to water and not by adding water to acid.
