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 industry. It is used in the processing of leather, production of gelatin. The physical properties such as density, melting point, PH, boiling point depends on the molarity or concentration of HCl.
Hydrochloric acid Structure – HCl
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 concentration 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 + 5Cl2 + 8H2O
2K2Cr2O7 + 14 HCl → 2KCl + 2CrCl3 + 3Cl2 + 7H2O
2. Hydrochloric acid reacts with salts like carbonates, hydrogen carbonates, sulphites etc. produces carbon dioxide gas and sulphur dioxde gas respectively.
Na2CO3 + 2 HCl → 2NaCl + H2O + CO2
NaHCO3 + HCl → NaCl + H2O + CO2
Na2SO3 + 2 HCl → 2NaCl + H2O + SO2
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, 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). 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 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
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