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Hydrochloric Acid Formula – Structure, Properties, Uses, Sample Questions

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  • Last Updated : 24 Jun, 2022

Hydrogen (H) has unique kind properties that are not like some other component on our planet. Close to 66% of our Universe’s mass is made out of this unique component. It is both electropositive as well as electronegative, as its structures have hydrogen particle H+ as well as hydride particle H. Hydrogen compounds are the main oxidants for some synthetic substances in the air and are associated with the patterns of numerous substance families. Hydrogen is utilized to make ammonia(NH3). 

Chlorine (Cl) is a greenish-yellow gas. It has a pungent odor-like smell. It has a boiling point of 239.11K and a melting point of 171.6K. The gas is harmful to nature, it is 2-5 times denser than air. Its atomic number is 17. It is the 2nd lightest halogen among all the elements. It has two isotopes, that are stable. By the process of oxidation, chlorine can be bleached, it needs moisture for its bleaching action. Chlorine when reacted with water forms hydrochloric acid and hypochlorous acid. 

Hydrochloric acid (HCl)

Hydrochloric acid (HCl) is an inorganic chemical, it is a strong corrosive acid. It is also known as hydrogen chloride or muriatic acid. It is a simple diatomic molecule, the chlorine atom and hydrogen connect over a single covalent bond and there exists a bond called a polar bond because the chlorine atom is more electronegative when we compare it with a hydrogen atom. It is strongly acidic in nature. It is colorless acid and has a different pungent smell.

The Formula of Hydrochloric acid

Hydrochloric acid has 2 elements named Hydrogen and Chlorine. Its chemical formula is,

H + Cl ⇢ HCl

Structure of Hydrochloric acid 

The hydrogen is combined with the chlorine atom with a covalent bond and has a planar structure. The structure of hydrochloric acid or muriatic acid is represented as,


Preparation of Hydrochloric acid

Hydrochloric acid is prepared by heating Sodium Chloride (NaCl) with concentrated sulphuric acid (H2SO4). The gas can be dried by passing through a concentration of sulphuric acid.

NaCl  +  H2SO4  →  NaHSO4  +  HCl

NaHSO4  +  NaCl →  Na2SO4  +  HCl 

Physical properties of Hydrochloric Acid

  • The Molecular weight/Molar Mass of hydrochloric acid is 36.458 g/mol.
  • It is a transparent liquid.
  • The boiling point and melting point depend on the concentration of HCl.
  • Hydrogen chloride is a colorless gas that has high odors.
  • Gaseous hydrogen chloride will react with the chloride which is formed by active metals and their hydroxide, carbonate, and oxides. Hydrogen chloride is inactive as well as totally dry.
  • Hydrochloric acid comprises acids like hydrogen gas is displayed in metal responses.
  • Glass hydrochloric acid is non-destructive. Hydrochloric corrosive is exceptionally destructive and assaults metals like platinum, gold, silver, mercury, tantalum, and so on.
  • It can deliver just a single proton as it is monoprotic.
  • It can totally disassociate to shape hydrogen and chloride particle in water.

Chemical Properties of Hydrochloric acid (HCl)

  • HCl can be oxidized with potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7) which gives chlorine gas.

2KMnO4 + 16 HCl → 2KCl + 2MnCl2 + 5Cl2 + 8H2O

2K2Cr2O7 +14 HCl → 2KCl + 2CrCl3 + 3Cl2 + 7H2O

  • Hydrochloric acid when reacted with salts like carbonates, hydrogen carbonates, and sulfites, it produces carbon dioxide gas and sulfur dioxide gas respectively.

Na2CO3 + 2 HCl → 2NaCl  + H2O + CO2

NaHCO3 +  HCl → NaCl  + H2O + CO2 

Na2SO3 + 2 HCl → 2NaCl  + H2O + SO2

  • A mixture of concentrated HCl and concentrated HNO3 in the ratio of 3:1 by volume is called Aqua regia. 
  • When HCl dissolves metals like gold and platinum they form their soluble chloride.

Uses of Hydrochloric acid

  • Purification of table salt and pH Control: This acid refines table salts. It is likewise helpful in the regulation of acidity of solutions and further, it is additionally used to control the pH of pharmaceutical items, drug items, water, and food varieties.
  • Production of oil: Hydrochloric acid is placed into a rock stone where the response of the rock stone formed as large-pore structures. This has huge help with oil production.
  • Cleaning agent: As a result of the corrosive nature of hydrophilic acid, it is valuable as a compound that assists with eliminating stains or rust from metals like copper and iron. It is being used for cleaning tiles in washrooms and kitchens and it is likewise helpful as a sanitizing specialist.
  • Pickling of steel: It is an interaction where diluted hydrochloric acid is being used for the expulsion of rust or iron oxide from steel or iron before it is processed into wire production, sheet and strip coating, and tin milling items.
  • Organic compounds: HCl is used in the production of Organic mixtures like vinyl chloride and dichloromethane which are helpful to produce PVC. It likewise produces organic compounds like ascorbic acid and pharmaceutical products.
  • Inorganic compounds: HCl is helpful in the preparation, of mixtures that are useful as water treatment synthetics. For instance, polyaluminium chloride (PAC), ferric acid, and aluminum carbohydrates are used in the treatment of water. It is additionally used in the regeneration of ion-exchange resins
  • Gastric Acid: Hydrochloric acid is an indispensable piece of gastric juice in the body which helps with indigestion. Dormant pepsinogen changes over into dynamic pepsin by hydrochloric corrosive in the stomach which helps assimilation by breaking the bonds connecting amino acids. This interaction is Proteolysis.

Sample Questions

Question 1: Is hydrochloric acid flammable?


Hydrochloric acid is an aqueous solution of acidic water, the hydrogen chloride. It reacts to poisonous or flammable materials by producing sulfides, carbides, borides, and phosphides. The production of flammable hydrogen gas reacts with several metals (including aluminum, zinc, calcium, magnesium, iron, nickel, and other alkalis by metals).

Question 2: How is hydrochloric acid formed?


Hydrochloric acid is formed by the combination of chlorine (Cl) and Hydrogen (H) gases, at temperatures above 250 °C (482 °F).

 H + Cl ⇢ HCl

Question 3: What are the uses of Hydrochloric acid?


It is used in the production of chlorides. It is used in rubber industries. It is used in the production of fertilizers. It is used in textile industries. It is used in the manufacture of dye. It is used for the production of oil, organic compounds, and inorganic compounds. It is used as a cleaning agent.

Question 4: Is hydrochloric acid a strong acid?


Yes, Hydrochloric acid is a strong solid acid. In water-heavy acids dissolves completely into their ions, while weak acids dissociate only partially. 

Question 5: Is HCl linear?


HCl molecule has a linear or tetrahedral geometry shape because it contains one hydrogen atom in the tetrahedral and three corners with three lone pairs of electrons. There is one H-Cl single bond at the HCl molecular geometry.

Question 6: What are the uses of HCl?


It is widely used in the laboratory as a reagent, in the processing of leather, the production of gelatin. It is used in the production of chlorides, rubber industries, and textile industries. It is also used in the production of fertilizers, oils, organic and inorganic compounds. It is used in the manufacture of dye and can also be used as a cleaning agent.

Question 7: What are the health hazards of Hydrochloric acid?


If we are exposed to HCl it may cause burning of the eyes, nose, and throat, cough, shortness of breath, nausea, vomiting, headache, and watery eyes. It can also cause severe damage like kidney or brain damage.

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