What is Hypochlorous Acid, and What are its Uses?

What is Hypochlorous Acid, and What are its Uses?

An acid is any substance or a compound that when added to a water solution can taste sour and can change the blue litmus paper to red colour, which is often used as an indicator to check the presence of acid.    Acids can also react with metals such as Fe (iron) liberating hydrogen. It can also react with many bases forming salts and this particular reaction is known as a neutralization reaction. Acid can also promote certain reactions chemically and this is usually termed acid catalysis. There are many examples of acids which include mineral acids that fall under inorganic substances. These are hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, and many more. Some organic substances include sulfonic acid, carboxylic acid, etc. These substances have one or more hydrogen atoms which are released as hydrogen ions (H+) according to Arrhenius theory. There are weak and strong acids. Strong acids dissociate completely when it is added to water in order to produce the maximum number of H+ ions whereas weak acids, on the other hand, do not dissociate completely but rather partially.

As being discussed earlier that there are many acids, in this article, we will purely discuss one acid i.e., Hypochlorous acid. This is a weak acid and is written as HOCl or HClO. This acid is also commonly known by many names namely as the Hydrogen hypochlorite or the other name given to it is the Chlorine hydroxide or simply the Hypochloric acid. This particular acid was found by Antoine Jerome  Balard who is a French Chemist back in the year 1834. The acid is known to be the oxyacid of chlorine and it consists of monovalent chlorine that acts either as an oxidizing or reducing agent. This acid is very much unstable and is used as a human metabolite. This acid is said to belong to a family containing reactive oxygen species which is also a hypochlorite’s conjugate acid.

Some of the well-known properties of the Hypochlorous Acid (HOCl) are given in the table below:

Formula HOCl
The molecular weight of Hypochlorous acid 52.457 g/mol
No. of hydrogen bond acceptor 1
Monoisotopic mass of HOCl 51.972 g/mol
No. of hydrogen bond donor 1

The structure of the Hypochlorous acid is depicted or shown in the figure below:

HOCl structure

This acid has many uses in products that are commonly used like:

  1. It is used in cosmetics and is mainly found in baby products.
  2. This acid is used in the sanitization of swimming pools.
  3. Hypochlorous acid is used for generatingenough amount of safe disinfectants.
  4. It is also used for marine sanitation where devices containing it convert seawater into HOCl.
  5. This is used in the medical field as well and is used as a wound caring agent. Another one is its usefulness in treating infections of various types for pets and human beings. In 2016 the U.S. Food and Drug Administration approved many products which contain hypochlorous acid as an ingredient actively as it is safe and effective for treating wounds.
  6. In chemical reactions, it is useful in the conversion of alkenes to chlorohydrins for various applications.

Some chemical reactionsinvolving the Hypochlorous acid:

  1. It partially dissociates ClO (anion hypochlorite)when added to certain aqueous solutions. The reaction is given as follows:

HClO⇌ClO + H+

The Hypochlorites are nothing but salts of this particular acid. The most common hypochloritesarethe NaClO called sodium hypochlorites which is the most common ingredient in bleach. When compared at standard conditions with chlorine it is a stronger oxidant.

2 HClO(aq) + 2H+ + 2e⇌ Cl2(g) + 2 H2O and E here is = +1.63 V

  1. This acid when it undergoes reaction with hydrochloric acid (HCl) it produces chlorine gas:

HClO + HCl → H2O + Cl2

What is going to happen if acids are added to an aqueous salt of this acid?

When acids are added to the aqueous salts of Hypochlorous acid like for example in the case of sodium hypochlorite, a commonly used hypochlorite in bleach solution commercially, chlorine gas is created whereby pushing the reaction to the left. Then, the chlorine gas dissolves easily into a simple water solution. Hence, it is used in the making of bleach.

  1. The third one is this acid is allowed toreact with amines for producing chloramines with water as a by-product.

NH3 + HClO→ NH2Cl + H2O

However, this acid is popular due to its common use as a safe disinfectant. Some examples of its use as a safe disinfectant include in the making of wash solutions like sanitizers and are commonly used in swimming pools sanitization. In these applications, the chlorine in the acid is applied to water for dissolving various reactive chemicals that are present in the solution.

For further studies refer to The P-block Elements from Class 12 Chemistry – Find All the Questions & Answers .

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