Hydrochloric acid also called muriatic acid is represented as HCl. This acid is a monobasic mineral acid which means every molecule releases only one hydrogen atom when it is dissolved in water, and it gets ionized. The hydrochloric acids use include
- To make aqua regia
- To generate Hydrogen gas
- In the manufacture of inorganic chemicals.
- In wastewater treatment.
- To clean ion exchange resins.
- For removal of metal stains
- Large scale production of polymers.
- In preparation for disinfectants.
- In metallurgy
- Laboratory reactions like titrimetry
- In the extraction of petroleum.
- For purification of table salt.
- Purification of sugar
- Tanning of leather
- For electric batteries
- As disinfectant to clean toilets.
- In medicine for achlorhydria
HCl is an ionic compound. Hydrogen chloride gets completely ionized in water and thus gives hydrogen ions. That’s why it behaves like an acid.
HCl = H+ + Cl–
Like Hydrobromic acid, Hydrochloric acid is a strong inorganic acid. It is a corrosive acid, and it’s colorless. HCl gas has a distinctively pungent smell, but when hydrogen chloride gas is dissolved in water to give hydrochloric acid, it becomes odorless. It is also called muriatic acid.
Hydrochloric acid is found in our stomach. HCl acid is made by parietal cells in the gastric glands of the stomach lining. This acid lowers the pH of the stomach, thus creating an acidic medium in which the stomach enzyme pepsin gets activated. Hydrochloric acid converts the pre-enzyme pepsinogen into the enzyme pepsin. This enzyme helps in the digestion of protein. The stomach lining also secretes mucus. This mucus protects the stomach lining from the corrosive effect of the hydrochloric acid. The acid is also responsible for killing many harmful microbes that enter the stomach along with the food. The pH of stomach fluid is usually around 4. When food enters the esophagus, HCl acid production increases, and the pH fall to a very acidic condition, as low as one or two.
Uses of hydrochloric acid
Hydrochloric acid is a very commonly used reagent and is used for many purposes like
1. Hydrochloric acid is used along with nitric acid in the production of aqua regia. This aqua regia is a mixture of the two acids. For every three parts of hydrochloric acid, one part of nitric acid is used. Aqua regia is a yellow fuming liquid, and it can dissolve inert metals like gold or platinum. It is used to clean jewelry or other items made of gold.
2. Hydrogen can be produced by corrosion of aluminum in Hydrochloric acid at different temperatures.
3. Hydrochloric acid is used to make many inorganic chemicals like poly aluminum chloride (PAC), iron (III) chloride, ferric acid(H2FeO4), etc.
4. HCl is a common chemical used in wastewater treatment. HCl is used to adjust the pH of water. It is used as an emulsion breaker in wastewater coming from industries. Since HCl is a powerful corrosive, it is also used to remove scale formation due to the salts in water.
5. HCl is used in the regeneration of ion exchange resins as it can rinse away the cations from the resins. Thus this reduces cost. The ion exchange method is used to remove the permanent hardness in water and convert it into soft water.
6. As it is a corrosive acid, it can be used to remove metal stains. It can also be used to watch metal surfaces. It can be used on metals like iron, copper or alloys like brass. It is used to clean the layer of rust formed on metal objects. But as it is a very strong acid solution it should be highly diluted with water; otherwise, the acid can eat through the metal and ruin the object. Thus HCl is a powerful cleaning agent.
7. HCl is used to make various useful polymers. In the chemical industry, it is used in the large scale production of PVC or polyvinyl chloride (CH2CHCl). It is used to produce polyurethane or to make plastic from starch. It is also used to make bisphenol A, which is used to produce plastic.
8. Hydrochloric acid is used in chlorine dioxide synthesis. Chlorine dioxide is a powerful disinfectant. It is commonly used as a bleaching agent.
2NaClO3 + 4HCl -> 2ClO2 + Cl2 + 2NaCl + 2H2O
9. Hydrochloric acid is used in various metallurgical processes like extraction of alumina, titanium dioxide, etc.
10. HCl is commonly used in many laboratory reactions like the identification of cations in salt, making salts like NaCl. It is also used to provide an acidic medium to facilitate specific reactions.
11. Hydrochloric acid is used for the production of mineral oil (petroleum). HCl acid is injected into a rock that may contain oil. The HCl acid acts like a corrosive and forms large-pore structures in the rock. This assists in oil production and extraction of oil.
12. This acid is used to purify table salt, which is sodium chloride (NaCl). In this method, the impure salt is dissolved in water where it ionized into sodium and chloride ions. Then the HCl is dissolved in water, and it also ionizes into H+ and Cl– Thus the chloride ion is common, and due to the common ion effect, NaCl ionization gets suppressed, and deposition of pure NaCl takes place.
13. HCl is used to regulate the acidity level or pH of industrial solutions. It is used to control and change the pH of commercial items like food or pharmaceutical products.
14. It’s used to purify sugar. We can extract xylose and glucose by acid hydrolysis of sugarcane juice. The other organic substances in the solution are removed by hydrochloric acid. This gives a solution in which the sugar concentration is more.
15. It is used in the leather tanning industry to process leather. HCl is used by tanneries to prevent the growth of bacteria on the leather as HCl can change the pH.
16. Hydrochloric acid is a powerful disinfectant and is commonly used for cleaning kitchens and bathrooms. It can reduce the pH and prevent the growth of bacteria.
17. HCl is used to clean completed brick structures by masons as it is a corrosive acid.
18. Hydrochloric acid is also used to make batteries as it is a powerful acid and dissociates readily to give hydrogen ions which act as charge carriers and complete the circuit generating current.
19. Achlorhydria is a condition wherein a person has an insufficient secretion of hydrochloric acid in his stomach. In such cases dilute HCl is used as medicine.