Why do you pour acid into water

Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated August 09, Featured Video. View Article Sources. Cite this Article Format. Helmenstine, Anne Marie, Ph. How to Mix Acid and Water Safely. Sulfuric Acid and Sugar Demonstration. List of the Strong Acids and Key Facts.

The reason this occurs is due to the large amount of energy released in the hydration reaction of sulfuric acid ions. Do not believe that heat comes from dissociation, as the dissociation of acids, bases, and salts always consumes energy. This happens with strong acids and bases. Strong means the acid almost complete dissociates into ions; e. When the dissociation occurs, it releases a great deal of heat i.

The reason you add acid to water is that if you add water to acid, the first drop of water reacts immediately, and the heat might be high enough to boil the water instantly, which could spray acid out of the container. This is more a problem with thermal mass. When dilution is performed, a small mass of the acid is combined with a much larger mass of water.

If the acid mass is in the receiving flask, there is initially a small mass of acid and water as the dilution is started. The energy released will heat the low mass mixture, with four joules of energy heating up one gram of the mixture by one degree Celsius.

If there isn't much mass, then the temperature change is dramatic and can easily cause the solution to boil, throwing droplets of concentrated sulfuric acid in the air. Sulfuric acid is extremely dangerous. It is intensely hygroscopic and will readily dehydrate carbohydrates and proteins by removing oxygens and hydrogens to make water molecules. This process will destroy the carbohydrates and proteins, including the materials that make up your skin and muscle. Concentrated sulfuric acid has disfigured many people who have been unlucky enough to come in contact with it.

Even when sulfuric acid is diluted the proper way, adding the acid to a volume of water can still result in an extremely hot mixture that might even boil. Good practice involves using a receiving flask that can contain a splashing acid water mixture, such as an Erlenmeyer flask, and even chilling the mixture during the dilution. A splash shield can also be placed between the worker and the dilution mixture and it could be done in a fume hood.

Heavy neoprene lab gloves, as well as eye protection, are recommended. Students in introductory chemistry classes rarely perform this dilution procedure, because of the high likelihood of accidents.

A large amount of heat is released when strong acids like sulfuric acid and HCl are mixed with water. If you add a little water to a lot of concentrated acid, the resulting solution is still concentrated. The hydration reaction uses all the water acid is the limiting reactant , generating a lot of heat.

The solution violently boils, spitting concentrated acid out of its container. If you add a little concentrated acid to a lot of water, water is the limiting reactant and the resulting solution is more dilute.

Here, all the acid reacts, but there is extra water to absorb the heat, lessening the chance of boiling. There are a few factors that make it better to add acid to water.

Also, some strong acids have a higher specific gravity or density than water. In this situation, the liquid readily boils and spits. On the other hand, if you pour acid on top of or into water, the water rises over the acid before mixing and contains the reaction. Sulfuric acid H 2 SO 4 is the most dangerous common acid to dilute.