The hydracids, also known as acidic acids or binary acids, are chemical compounds that arise from the combination of hydrogen atoms with halogen atoms (fluorine, chlorine, bromine or iodine: group VIIA of the periodic table), or with atoms of amphogenic elements or chalcogens, such as sulfur, selenium or tellurium (group VIA in the table). For instance: hydrochloric acid, hydrobromic acid, hydroiodic acid.
Hydracids formed with halogens they act with oxidation state -1 and the formula that represents them is HX. Hydracids formed with amphogens act with oxidation state -2 and are schematized with the formula H2X.
Characteristics of hydracids
- Hydracids do not contain oxygen. The compounds thus formed are binary and acidic in aqueous solutions.
- Other nonmetals also form binary compounds with hydrogen, but not necessarily acidic. For example: ammonia combines nitrogen with hydrogen and when it dissolves in water the pH increases, not decreases.
- Hydracids are usually named both with the traditional nomenclature, for example: hydrochloric acid, and with the Stock nomenclature. For example: hydrogen chloride.
It is important to clarify that when the formula of a hydracid, it must be represented that it is in aqueous solution of the form: HX(ac). If this is not done, then what is being represented is a hydrogen halide, which have the same molecular formula as the hydracids, but are gaseous (HX(g)).
The hydrogen halides (so called those that comprise a halogen in direct combination with hydrogen) are strong acids (except hydrogen fluoride). The acidic force (given by the ability to release protons when dissociating in solution) increases as the atomic mass increases, that is, as the periodic table of elements is traversed from top to bottom in the group. Concentrated solutions of these acids often release white smoke.
Uses of hydracids
Hydracids are used in different chemical industries. They are often used to formulate hygiene and household cleaning products. For example, they are important components of soaps, at low concentrations.
They are also present in toiletries and personal hygiene such as shampoos, toothpastes, hair conditioners, and certain cosmetics. At higher concentrations they are used to unclog pipes.
To digest food, our body synthesizes gastric juice, which is released in the stomach. This juice contains various enzymes (pepsin, renin, gastric lipase) and hydrochloric acid, produced by the parietal cells of said organ.
This acid causes the stomach’s pH to be around 2, or even slightly lower. Under these conditions, food degradation is possible.
Examples of hydracids
There are only seven hydracids and they are:
- Hydrochloric acid, HCl(ac)
- Hydrogen sulfide, H2S(ac)
- Hydrobromic acid, HBr(ac)
- Selenhydric acid, H2I know(ac)
- Hydroiodic acid, HI(ac)
- Tellurhydric acid, H2Tea(ac)
- Hydrofluoric acid, HF(ac)