Hydrochloric acid - HCl

What is Hydrochloric acid?

Hydrochloric acid is an inorganic chemical. It is a strong corrosive acid with a chemical formula HCl. It is also known as hydrogen chloride or muriatic acid.

When hydrogen chloride is dissolved in water HCl is formed. It is a simple diatomic molecule. The hydrogen and chlorine atom are connected with a single covalent bond. The bond between them is polar as the chlorine atom is more electronegative when compared with the hydrogen atom.

It is strongly acidic. It is colourless and viscous. It is corrosive and has a distinctively pungent smell. It is widely used as a laboratory reagent and in industry. It is used in the processing of leather, the production of gelatin. The physical properties such as density, melting point, PH, and boiling point depends on the molarity or concentration of HCl.

Table of Contents

Hydrochloric acid Structure – HCl

Hydrochloric acid structure

Preparation of Hydrochloric acid – HCl

In the laboratory, as well as on commercial-scale hydrogen chloride is prepared by heating sodium chloride with concentrated H2SO4. The gas can be dried by passing through a concentration of sulphuric acid.

NaCl  +  H2SO4  →  NaHSO4  +  HCl 

NaHSO4  +  NaCl →  Na2SO4  +  HCl


Properties of Hydrochloric acid – HCl

Hydrogen chloride is a highly odorous, colourless gas. Gaseous hydrogen chloride responds to the chlorides formed by active metals and their oxides, hydroxides, and carbonates. Such reactions only occur readily in the presence of humidity. Hydrogen chloride is completely dry and is very unreactive.

Hydrochloric acid reactions are those of common strong acids, such as: metal reactions in which hydrogen gas is displaced, reactions with simple (metal) oxides and hydroxides that are neutralized with the forming of a metal chloride and water, and reactions with weak acid salts in which the heavy acid is displaced.

HCl Hydrochloric acid
Molecular Weight/ Molar Mass 36.458 g/mol
Appears Transparent liquid
Boiling Point Depends on the concentration
Melting Point Depends on the concentration

Chemical Properties of Hydrochloric acid – HCl

1. HCl can be oxidized by potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7) liberated chlorine gas.

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

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

2. Hydrochloric acid reacts with salts like carbonates, hydrogen carbonates, sulphites etc. producing carbon dioxide gas and sulphur dioxide gas respectively.

Na2CO3 + 2 HCl   →  2NaCl  + H2O +  CO

NaHCO3 +  HCl   →  NaCl  + H2O +  CO 

Na2SO3 + 2 HCl   →  2NaCl  + H2O +  SO

3. A mixture of conc. HCl and conc. HNO3 in the ratio of 3:1 by volume is called Aqua regia. It can dissolve metals like gold and platinum to form their soluble chloride.

HCl- Hydrochloric acid in Stomach

Stomach secretions consist of hydrochloric acid, several enzymes and a mucus coating which protects your stomach lining. Hydrochloric acid helps the body break down foods such as calcium, and digest and drink them. It also eliminates stomach bacteria and viruses, thereby protecting your body from infection. Stomach acid is composed of hydrochloric acid (HCl), potassium chloride (KCl), and sodium chloride (NaCl). The hydrochloric acid concentration in the stomach is approximately 0.5 percent, or 5,000 parts per million.

A balanced stomach’s pH is generally 1.0-2.0. This low stomach fluid level normally leaves it free from microbes. Around the same time, though, these pH levels place stomach acid almost in the same category as battery acid, which can melt steel.

HCl Uses (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 in the refining of metals
  • It is used in the production of organic compounds like PVC
  • It is used to regulate the PH of solutions
  • It is used in the stimulation of oil production

Frequently Asked Questions – FAQs


What is the hydrochloric acid used for?

Hydrochloric acid is an effective chemical reagent used in the manufacture of polyvinyl chloride for plastics and industrial chemicals. Diluted hydrochloric acid is frequently used as a descaling agent in households. Hydrochloric acid is used as a food additive in the food industry, and in gelatin processing.


Is hydrochloric acid flammable?

Hydrochloric acid is an aqueous solution of acidic water, hydrogen chloride. Reacts to poisonous or flammable materials by producing sulfides, carbides, borides, and phosphides. To produce flammable hydrogen gas, reacts with several metals (including aluminium, zinc, calcium, magnesium, iron, nickel, and other alkali metals).


What neutralizes hydrochloric acid?

Neutralize hydrochloric acid, such as sodium bicarbonate (baking soda), with an alkali (base). Apply more baking soda, before it starts fizzing. It ensures that the hydrochloric acid is neutralized, and can now be flushed with massive quantities of water into the drain.


How is HCl produced in the stomach?

HCl is formed by the abdominal parietal cells. This channel uses ATP energy to exchange in-stomach potassium ions with parietal cell hydrogen ions. This leads to the presence of both hydrogen and chloride ions within the lumen of the stomach.


Is hydrochloric acid a strong acid?

Underwater, heavy acids dissociate completely into their ions, while weak acids dissociate only partially. Hydrochloric acid, nitric acid, sulphuric acid, hydrobromic acid, hydroiodic acid, perchloric acid, and chloric acid are solid acids.

Also, Read:

Nitric Acid Acetic Acid
Ascorbic Acid Sulfuric Acid

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