When mixing water and acid, which is the correct procedure?

The most appropriate procedure when mixing water and acid is to always add the concentrated reagent (acid) to water. This is a crucial safety practice in chemistry because when acid is added to water, the dilution of the acid leads to the release of heat. If water were to be added directly to concentrated acid, the reaction can be exothermic and may result in the acid splattering or boiling over, posing significant safety hazards to the individual handling the materials.

By adding the acid to water, the water molecules can absorb the heat generated during the mixing process, which minimizes the risk of a violent reaction. This method ensures that the concentrated acid is properly diluted while controlling the temperature rise, making it a safer practice in laboratory environments. Because of this fundamental principle in laboratory safety, it is critical to follow the correct sequence of mixing to prevent accidents or injuries.