What is Strong Acids and their List - Definition, Examples with FAQs

Q: Which of the following is strong acid? HCl, CH3COOH, NaOH.

HCl is a strong acid whereas CH 3 COOH is a weak acid. NaOH is a strong base.

Q: Which is the strongest acid?

The strongest acid is fluoroantimonic acid HSbF 6 and it is made from compounds like hydrogen fluoride and antimony pentafluoride. It is also called superacids. The Hammet acidity function H 0 of this compound is very high.

What is Strong Acids and their List - Definition, Examples with FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:47 PM IST

Before going to discuss strong acids first we need to know what is strong acids and strong bases.

Strong Acids and Strong Bases

Strong acids are those acids that dissociate or break down completely in their ions. Strong acid examples are HCl, HBr, etc. Strong bases are also bases that dissociate or break down completely in their ions in solution. Example NaOH, KOH, etc.

What is a Strong acid?

Strong acid definition: Strong acids are those compounds that can be completely dissociated into their constituent ions, that is their conjugate base and a proton when they are dissolved in water. The seven most common examples of strong acids are;

Hydrochloric acid (represented by using the chemical formula HCl)
Hydrobromic acid (represented by using the chemical formula HBr)
Hydroiodic acid or hydriodic acid (represented by using the chemical formula HI)
Sulfuric acid (represented by using the chemical formula H2SO₄)
Nitric acid (represented by using the chemical formula HNO₃)
Chloric acid (represented by using chemical formula HClO₃)
Perchloric acid (given by the chemical formula HClO₄)

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Strong Acids and Strong Bases
What is a Strong acid?
List of strong acids
Strong Bases

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Acid strength is defined as the property of an acid that is represented as HA breaks down to form the H⁺ ions. That is,

HA→H⁺+A^-

A strong acid like HCl breaks down completely as shown below,

HCl→H⁺+Cl^-

While a weak acid will be dissociated only partially and thereby exist in an equilibrium state.

List of strong acids

Strong acids examples are following. And strong acid names are given below.

1. Hydrochloric Acid (HCl)

Hydrochloric acid, HCl (strong acid) could be a water solution of hydrogen chloride gas. It is also known as muriatic acid with the chemical formula HCl. HCl is a type of inorganic acid, colorless with a pungent smell. It has also been given the name corrosive acid due to its high acidity. HCl is mainly used in steel production, as a household cleaner, food production, and processing, etc. HCl dissociates to form a chloride ion and the hydronium ion. It is the main component of the gastric acid that is present in the digestive tracts of almost all animal species and it helps in the digestion of foods.

2. Hydrobromic Acid (HBr)

Hydrobromic acid (strong acid) is a solid acid formed by the reaction of hydrogen bromide with water. Hydrobromic acid is a stronger acid than hydrochloric acid because of its high pKa value. It is the strongest mineral acid. It is mainly used for the production of certain inorganic bromides, like calcium, zinc, and sodium. It acts as a catalyst in several alkylation reactions.

3. Hydroiodic Acid (HI)

Hydroiodic acid (strong acid) is a solution of hydrogen iodide and water. It is a strong acid and dissociates completely to form iodides and hydrogen ions. It is a colorless acid with an acrid odor. HI is used as a chemical reagent, Cativa process is the one among them and it acts as a cocatalyst in this process. HI can also act as a reducing agent in many reactions.

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4. Sulphuric Acid (H₂SO₄)

Sulphuric acid (strong acid) is a mineral acid containing oxygen, sulfur, and hydrogen with a molecular formula H₂SO₄. It is a colorless, odorless liquid with high viscosity. The main property of sulphuric acid is it is soluble in water and is highly reactive with water vapor so it is known to be hygroscopic. It is corrosive and highly dehydrating in nature. Due to high acidity while using sulphuric should be very careful even at low concentration it will cause serious damage to the outer skin and internal portion. It is mainly used for the production of detergents, dyes, pharmaceuticals, insecticides, etc.

5. Nitric Acid (HNO₃)

Nitric acid (strong acid) is acid-containing nitrogen, oxygen, and hydrogen with a chemical formula HNO₃. It is a highly corrosive mineral acid. Due to its high oxidizing nature, it is widely used in nitration reactions which involve the addition of a nitro group to a given chemical compound mainly organic compound like benzene. It will be colorless when prepared freshly turns yellow color while getting older. It is known to have an extremely suffocating, acrid odor. Nitric acid is mainly used for the production of fertilizers, explosives, nylon precursors, etc.

6. Perchloric Acid (HClO₄)

Perchloric acid (strong acid) is acid-containing hydrogen, chlorine, and oxygen with a chemical formula HClO₄. It is a water-based colorless solution. Its acidic strength is high and perchloric acid is a stronger acid than sulphuric acid and nitric acid. It is corrosive and is highly explosive compounds are formed. It is high oxidizing so it should be handled carefully in reactions involving the participation of oxygen. It is mainly used for the production of ammonium perchlorates. Another important use of perchloric acid is, it can be used as an eluent in the ion-exchange chromatography process and also used in the electropolishing process.

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7. Chloric Acid (HClO₃)

Chloric acid (strong acid) is a mineral acid containing hydrogen, chlorine, and oxygen with a chemical formula HClO₃. It is an oxoacid of chlorine with highly acidic. It is highly oxidizing in nature also. Above a particular concentration, it will dissociate to form different products. As it readily undergoes disproportionation, it is thermodynamically unstable also. It is used as a catalyst to make other chemical species. It is a highly corrosive acid for metals and tissues. One should be very careful while handling acids.

Strong Bases

Strong bases are also bases that dissociate or break down completely in their ions in solution. Example NaOH, KOH, etc.

A strong acid like KOH breaks down completely as shown below,

KOH→K⁺+OH^-

While a weak base will be dissociated only partially and thereby exist in an equilibrium state.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. Which of the following is strong acid? HCl, CH3COOH, NaOH.

HCl is a strong acid whereas CH₃COOH is a weak acid. NaOH is a strong base.

2. Is chlorine an acid or base?

When chlorine is added to water acid is formed.

3. What are strong acids and weak acids?

Strong acids are those acids that are completely dissociated in water example HCl, HBr, etc. While weak acids are those acids that are incompletely dissociated in water example of it is HF that is hydrofluoric acid.

4. Q. How many acids are there?

There are mainly two types of acids organic acid and mineral acids. The acid which is formed from organic compounds is organic while those formed from minerals are mineral acid.

5. Which is the strongest acid?

The strongest acid is fluoroantimonic acid HSbF₆ and it is made from compounds like hydrogen fluoride and antimony pentafluoride. It is also called superacids. The Hammet acidity function H₀ of this compound is very high.

6. Strong acid and strong base example?

Strong acids include HCl, HBr, etc. And strong bases include NaOH, KOH, etc.

7. Why HCl is a strong acid?

HCl dissociates completely in water so it is a strong acid.

8. Strong acid weak acid example?

HCl, HBr, HI, etc. are strong acids while HF could be a weak acid.

9. Is Nitric acid strong or weak?

Nitric acid decomposes completely in water so it is a strong acid.

10. Is H2SO4 a strong acid?

Sulphuric acid dissociates completely in water to form corresponding ions do it is a strong acid.

11. King of acid is?

Sulphuric acid is named as the king of acid.

12. Which is the most corrosive acid?

HF, hydrofluoric acid is the most corrosive acid because of its high penetrating nature in human tissues.

13. Can you list some common strong acids?

Common strong acids include:

14. How do strong acids contribute to acid rain?

Strong acids like sulfuric acid (H2SO4) and nitric acid (HNO3) are major components of acid rain. They form when sulfur dioxide and nitrogen oxides from industrial emissions react with water in the atmosphere, creating these strong acids that fall as precipitation.

15. What is the role of strong acids in the stomach?

The stomach produces hydrochloric acid (HCl), a strong acid that aids in digestion. It helps break down food, activates digestive enzymes, and kills harmful bacteria. However, the stomach lining has protective mechanisms to prevent damage from this strong acid.

16. What is the difference between monoprotic and polyprotic strong acids?

Monoprotic strong acids, like HCl, donate one proton (H+) per molecule when they dissociate. Polyprotic strong acids, like H2SO4, can donate multiple protons per molecule. Sulfuric acid, for example, can donate two protons in two separate steps.

17. How do strong acids react with metals?

Strong acids react vigorously with most metals, producing hydrogen gas and a metal salt. The reaction is often exothermic (releases heat) and can be quite rapid, especially with more reactive metals like sodium or magnesium.

18. What is the difference between a strong acid and a concentrated acid?

A strong acid refers to the degree of dissociation in water, while concentration refers to the amount of acid dissolved in a given volume of solution. A strong acid can be dilute (low concentration) or concentrated (high concentration), but it will always completely dissociate.

19. How do strong acids affect proteins?

Strong acids can denature proteins by disrupting their hydrogen bonds and changing their three-dimensional structure. This process can alter or destroy the protein's function, which is why strong acids are so damaging to living tissues.

20. What is the concept of leveling in strong acids?

The leveling effect occurs when a strong acid is dissolved in water. Water acts as a base, accepting protons from the acid. All strong acids in aqueous solution essentially become as strong as the hydronium ion (H3O+), which is the strongest acid that can exist in water.

21. How do strong acids affect indicators?

Strong acids cause dramatic color changes in pH indicators due to their high concentration of hydrogen ions. For example, they turn blue litmus paper red and cause methyl orange to change from yellow to red.

22. Why are strong acids considered dangerous?

Strong acids are dangerous because they are highly corrosive and reactive. They can cause severe chemical burns to skin and eyes, damage materials, and react violently with certain substances. Their complete dissociation results in a high concentration of hydrogen ions, making them particularly hazardous.

23. How do strong acids participate in neutralization reactions?

Strong acids participate in neutralization reactions by completely donating their protons to a base. This results in the formation of water and a salt. The reaction is typically exothermic and goes to completion due to the full dissociation of the strong acid.

24. How do strong acids affect the solubility of certain compounds?

Strong acids can increase the solubility of certain compounds, especially those that are basic or contain carbonate groups. This is because the acid can react with these compounds, converting them into more soluble forms or breaking them down into simpler, more soluble components.

25. How do strong acids affect carbonates?

Strong acids react vigorously with carbonates, producing carbon dioxide gas, water, and a salt. This reaction is often used as a test for carbonates, as the production of CO2 causes visible bubbling or effervescence.

26. Why is sulfuric acid considered both a strong acid and a dehydrating agent?

Sulfuric acid is a strong acid due to its complete dissociation in water. It's also a powerful dehydrating agent because it has a strong affinity for water, capable of removing water molecules from other compounds through reactions like esterification or dehydration synthesis.

27. What is the role of strong acids in the production of fertilizers?

Strong acids, particularly sulfuric and nitric acids, are crucial in fertilizer production. They are used to convert raw materials like phosphate rock into soluble forms that plants can absorb. For example, sulfuric acid is used to produce phosphoric acid, a key component in many fertilizers.

28. What are strong acids?

Strong acids are substances that completely dissociate (break apart) into ions when dissolved in water. They release all of their hydrogen ions (H+) in solution, making them highly reactive and corrosive.

29. How do strong acids differ from weak acids?

Strong acids completely dissociate in water, while weak acids only partially dissociate. Strong acids have a higher concentration of hydrogen ions in solution, making them more reactive and having lower pH values compared to weak acids.

30. What is the pH range of strong acids?

Strong acids typically have pH values below 1. The exact pH depends on the concentration of the acid, but it's generally much lower than that of weak acids.

31. Why is hydrochloric acid considered a strong acid?

Hydrochloric acid is considered a strong acid because it completely dissociates in water, releasing all of its hydrogen ions (H+) and chloride ions (Cl-). This complete dissociation results in a high concentration of H+ ions in solution, making it highly acidic.

32. How does the strength of an acid relate to its Ka value?

The acid dissociation constant (Ka) is a measure of an acid's strength. Strong acids have very large Ka values (typically greater than 1), indicating complete dissociation. Weak acids have much smaller Ka values, usually less than 1.

33. How do strong acids conduct electricity?

Strong acids are excellent conductors of electricity in aqueous solution because they completely dissociate into ions. These free ions can carry electrical charge, allowing the solution to conduct electricity effectively.

34. What is the relationship between strong acids and their conjugate bases?

Strong acids have very weak conjugate bases. This is because the stronger an acid is, the less likely it is to accept a proton back once it has donated one, making its conjugate base very weak.

35. What is the concept of superacids?

Superacids are acids stronger than 100% sulfuric acid. They have an extremely high ability to donate protons, even more so than conventional strong acids. Examples include fluoroantimonic acid and magic acid. They are used in specialized chemical reactions and research.

36. How do strong acids interact with amphoteric substances?

Amphoteric substances can act as both acids and bases. When they interact with strong acids, they behave as bases, accepting protons from the acid. This versatility allows amphoteric substances to react in different ways depending on the pH of their environment.

37. What is the role of strong acids in battery technology?

Strong acids, particularly sulfuric acid, play a crucial role in lead-acid batteries. The acid serves as the electrolyte, facilitating the flow of ions between the electrodes. The concentration of the acid changes as the battery charges and discharges, affecting its performance.

38. How do strong acids contribute to the weathering of rocks?

Strong acids contribute significantly to chemical weathering of rocks. They can dissolve minerals, especially those containing calcium or magnesium. Acid rain, containing sulfuric and nitric acids, accelerates this process, breaking down rocks and altering landscapes over time.

39. What is the importance of strong acids in the production of plastics?

Strong acids are essential in various stages of plastic production. For example, sulfuric acid is used in the production of nylon, while hydrochloric acid is used in PVC manufacturing. These acids participate in polymerization reactions and help create the desired molecular structures.

40. How do strong acids affect enzyme activity?

Strong acids typically denature enzymes by disrupting their three-dimensional structure. This denaturation occurs because the acid alters the pH far from the enzyme's optimal range, disrupting hydrogen bonds and other interactions that maintain the enzyme's active conformation.

41. What is the role of strong acids in the petroleum industry?

Strong acids, particularly sulfuric acid, are used in various processes in the petroleum industry. They're used in oil refining for processes like alkylation (to produce high-octane gasoline components) and in the removal of impurities from crude oil.

42. How do strong acids participate in esterification reactions?

Strong acids catalyze esterification reactions between alcohols and carboxylic acids. They protonate the carboxylic acid, making it more electrophilic and thus more reactive towards the alcohol. This results in the formation of an ester and water.

43. What is the concept of Brønsted-Lowry acids in relation to strong acids?

In the Brønsted-Lowry theory, acids are proton donors. Strong acids are excellent proton donors, readily giving up their protons in solution. This high tendency to donate protons is what makes them strong acids in this theoretical framework.

44. How do strong acids affect the human body if ingested?

Ingestion of strong acids can cause severe damage to the digestive system. They can cause chemical burns to the mouth, throat, and esophagus, potentially leading to perforation of these organs. Strong acids can also disrupt the body's pH balance, leading to systemic effects if absorbed into the bloodstream.

45. What is the role of strong acids in the production of pharmaceuticals?

Strong acids are used in various stages of pharmaceutical production. They can be used as reagents in synthesis reactions, for pH adjustment, in the production of salt forms of drugs, and in the extraction and purification of active pharmaceutical ingredients.

46. How do strong acids contribute to the formation of coordination compounds?

Strong acids can play a role in the formation of coordination compounds by providing an acidic environment that facilitates ligand exchange. They can also protonate ligands, changing their binding properties, or act as ligands themselves in some cases (like chloride from HCl).

47. What is the concept of acid strength in non-aqueous solvents?

The strength of an acid can change in non-aqueous solvents. Some acids that are strong in water may behave as weak acids in other solvents, and vice versa. This is because acid strength depends on the solvent's ability to stabilize the conjugate base of the acid.

48. How do strong acids affect the boiling point of water?

Strong acids generally increase the boiling point of water when dissolved in it. This is due to the colligative properties of solutions – the addition of ions (from the dissociated acid) disrupts the water's intermolecular forces, requiring more energy to bring the solution to a boil.

49. What is the role of strong acids in the production of explosives?

Strong acids, particularly nitric acid, are crucial in the production of many explosives. For example, nitric acid is used in the nitration process to produce nitroglycerin and TNT. Sulfuric acid is often used in combination with nitric acid in these processes.

50. How do strong acids interact with bases in titration experiments?

In acid-base titrations, strong acids react completely with bases. The reaction proceeds until one reactant is fully consumed. The equivalence point of such a titration occurs at a pH below 7, and the titration curve shows a sharp change in pH near the equivalence point.

51. What is the concept of Lewis acids in relation to strong acids?

While most strong acids are Brønsted-Lowry acids (proton donors), they can also behave as Lewis acids (electron pair acceptors). For example, the H+ ion from a strong acid can accept an electron pair from a base, forming a coordinate covalent bond.

52. How do strong acids contribute to the extraction of metals from ores?

Strong acids are used in hydrometallurgy to extract metals from their ores. For example, sulfuric acid is used to extract copper from its sulfide ores. The acid dissolves the metal, forming a solution from which the pure metal can be recovered through various processes.

53. What is the role of strong acids in food preservation?

While strong acids themselves are too corrosive for direct use in food, their salts or diluted forms are used in food preservation. For example, sodium benzoate (derived from benzoic acid) is used as a preservative. The acidity helps prevent microbial growth and extends shelf life.

54. How do strong acids affect the solubility of gases in water?

Strong acids can affect the solubility of gases in water in various ways. For some gases, like CO2, the presence of strong acids can increase solubility by reacting with the dissolved gas. For others, the high concentration of ions from the dissociated acid can decrease gas solubility through the salting-out effect.

55. What is the concept of acid anhydrides in relation to strong acids?

Acid anhydrides are compounds that can form strong acids when they react with water. For example, sulfur trioxide (SO3) is the acid anhydride of sulfuric acid (H2SO4). When SO3 reacts with water, it forms H2SO4, a strong acid.

56. How do strong acids participate in redox reactions?

Strong acids can participate in redox reactions in several ways. They can act as oxidizing agents, accepting electrons from other species. For example, concentrated sulfuric acid can oxidize metals. They can also provide an acidic environment that facilitates other redox reactions.

57. What is the role of strong acids in the production of dyes?

Strong acids play crucial roles in dye production. They are used in various synthesis steps, such as in diazotization reactions to produce azo dyes. Sulfuric acid is often used in the production of vat dyes, while hydrochloric acid is used in the synthesis of triphenylmethane dyes.

58. How do strong acids affect the conductivity of solutions?

Strong acids significantly increase the electrical conductivity of solutions because they completely dissociate into ions. These ions can carry electrical charge through the solution. The higher the concentration of the strong acid, the greater the conductivity of the solution.

59. What is the concept of polyprotic dissociation in strong acids?

Polyprotic strong acids, like sulfuric acid, dissociate in steps. For H2SO4, the first dissociation (H2SO4 → H+ + HSO4-) is complete, making it a strong acid. The second dissociation (HSO4- → H+ + SO42-) is much weaker. This stepwise dissociation affects the acid's behavior in solution.

60. How do strong acids contribute to the formation of buffer solutions?

While strong acids themselves don't form buffers (as they dissociate completely), they can be used to create buffer solutions when combined with their conjugate bases. For example, a mixture of hydrochloric acid and sodium chloride can form a buffer solution at certain concentrations.

61. What is the role of strong acids in the production of biodiesel?

Strong acids, particularly sulfuric acid, are used as catalysts in the production of biodiesel. They catalyze the transesterification reaction between triglycerides (from vegetable oils or animal fats) and methanol, producing fatty acid methyl esters (biodiesel) and glycerol.

62. How do strong acids affect the properties of polymers?

Strong acids can significantly affect polymer properties. They can cause degradation of certain polymers through hydrolysis, breaking polymer chains. In some cases, they can induce cross-linking. Strong acids are also used in the synthesis of some polymers, influencing their final properties.