What is hydrolysis? (with photos)

Hydrolysis is used in the production of soap.

Hydrolysis is a type of chemical reaction that takes place between water and another compound. During the reaction, chemical bonds are broken in both molecules, causing them to separate. The water molecule splits to form positively charged hydrogen ions (H + ) and negatively charged hydroxide (OH – ), and the other molecule splits into two simpler sections, also with positive and negative charges. H+ and OH -ions attached to each of these sections. These reactions occur when some ionic compounds, for example certain acids, bases and salts, dissolve in water; they are involved in essential life processes; they are used in some important industrial processes such as soap making; and they play an important role in the weathering of rocks.

ionic compounds

Hydrolysis is a reaction between water molecules and other chemical compounds.

Ionic compounds can be acids, bases or salts, which are compounds that result from the reaction of an acid and a base. They are composed of positively charged cations and negatively charged anions. When they are dissolved in water, they break down into their cations and anions. Anions from weak acids and cations from weak bases will react with water to some extent, resulting in hydrolysis.

In ATP hydrolysis, adenosine triphosphate (ATP) is converted to adenosine diphosphate (ADP) by the loss of a phosphoanhydro group.

Where a salt is the product of a strong acid and a weak base, the cation of the base will hydrolyze to water. For example, ammonium chloride (NH 4 Cl) is the salt of a weak base – ammonia (NH 3 ) – and a strong acid – hydrochloric (HCl). When dissolved in water, it splits into cations and anions – NH 4 + and Cl – , respectively. The cation, however, will react with water to some extent, losing a hydrogen ion:

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NH 4 + + H 2 O NH 3 + H 3 O +

Since this reaction produces hydronium ions (H 3 O + ), the resulting solution is acidic. When a salt is the product of a strong base and a weak acid, the anions of the acid will react with water by accepting hydrogen (H + ) ions, leaving hydroxide (OH – ) ions, which gives an alkaline solution. The salt of a strong acid and a strong base do not hydrolyze because the anion of the acid and the cation of the base do not react with water.


Many processes essential to life involve hydrolysis. An example is the release of energy by the molecule adenosine triphosphate (ATP). Cells use this compound to store energy, which can be released when needed. The molecule has three phosphate groups (PO 4 – ), but it can lose one of these groups when reacting with water. This reaction actually consumes a small amount of energy, but much more is released by the subsequent reactions of the free phosphate group.

Hydrolysis also plays a vital role in breaking down food into easily absorbed nutrients. Most organic compounds in foods do not readily react with water, and a catalyst is often needed to allow these processes to take place. The organic catalysts that aid reactions in living organisms are known as enzymes. In the body, enzymes such as lipases, carbohydrases, and proteases catalyze reactions with fats, carbohydrates, and proteins with water.

An example of hydrolysis is the breakdown of starch, which is catalyzed by the enzyme amylase. Starch is broken down into smaller molecules, which consist of the sugar known as maltose. Maltose can then be broken down into glucose molecules under the influence of the maltase enzyme. In each case, water participates in the process, splitting and adding a hydroxyl group and a hydrogen ion to the new molecules formed on either side of the broken bond.

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Many industrial procedures require various substances to be hydrolyzed to create useful products. Often, however, the raw materials for these processes do not readily react with water molecules, so the reactions are aided by a variety of means, such as high pressure, high temperatures, and catalysts. Laboratory hydrolysis usually requires the use of a catalyst, which is typically a strong acid or alkali.

Hydrolysis has long been used in soap production. During this process, known as saponification, the fat is hydrolyzed in a reaction with water and the strong alkali, sodium hydroxide. The reaction produces fatty acid salts, commonly known as soap. Saponification sometimes occurs in old oil paintings, when the fatty acids in the oil paint react with the metals in the paint’s pigments. This can cause deposits and white bumps to develop on the surface of the paintings, although it is not known why this only occurs in some artworks and not in others.


Hydrolysis is an important process in the weathering of rocks. Various silicate minerals, such as feldspar, undergo slow hydrolysis reactions with water, forming clay and silt, along with soluble compounds. This process is important in the formation of soils, and in making essential minerals available to plants.

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