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Sulfuric Acid – H2SO4

Last Updated : 19 Dec, 2023
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Sulfuric Acid or Sulphuric Acid is a mineral acid consisting of one Sulfur, four Oxygen, and two Hydrogen atoms. The chemical or molecular formula of Sulfuric Acid is H2SO4. Sulfuric Acid is one most important commercially used chemicals. It is also known as Mattling acid or Hydrogen Sulfate or Vitriol. Sulphuric acid is a very strong acid and viscous liquid. It is a colorless, odorless, oily liquid, and corrosive in nature. Sulfuric acid is a component of acid rain as it is soluble in water.

Sulfuric acid is a highly acidic liquid. As a result, it is used for the cleaning of metals, the extraction of impurities from oil, the production of chemicals such as nitric acid and hydrochloric acid, and the manufacture of dye, medicines, detergents, and explosives, among other processes. The molar mass of Sulfuric Acid is 98.079 g/mol. The density of Sulfuric acid is 1.83 g/cm3. The H2SO4 molecule is covalent and has a tetrahedral structure and monoclinic crystal structure.

What is Sulfuric Acid?

Sulfuric acid is a highly reactive chemical. Sulfuric acid is used in many industries like lead-based automobile batteries, the production of various chemicals, glue, and explosives, the refinement of petroleum, the curing of metal, etc. Hence, due to these wide applications, it is referred to as the “King of Chemicals“. The chemical formula for Sulfuric or Sulphuric Acid is H2SO4

As shown below, Sulfuric Acid (H2SO4) is a covalent compound that consists of a Sulfur atom, which is attached to two Oxygen atoms and two Hydroxyl molecules (-OH).

Sulfuric Acid


Properties of Sulfuric Acid (H2SO4)

Physical Properties of Sulfuric Acid

  • H2SO4 is a viscous, thick, colorless, and oily liquid
  • Sulfuric acid has a density of 1.84 g/mL, a boiling point of 337 °C, and a melting point of 10 °C. 
  • Concentrated sulfuric acid is 98% in water, and is the most stable form. Many other concentrations, with different names, are available for various purposes like Battery acid which is 29–32%, chamber acid which is 62-70%, and tower acid which is 78-80%.
  • It has a specific gravity of 1.84 at 298 K.
  • It turns blue litmus red and the pH values of sulphuric acid in mmol/l are mentioned in the table below,
pH values  1 mM 10 mM 100 mM
Sulphuric acid (in mmol/l) 2.75 1.87 1.01
  • It is highly corrosive, making it dangerous to touch.

Chemical Properties of Sulfuric Acid

  • H2SO4 is a strong acid that completely dissociates into ions in its aqueous solution as,

H2SO4  ⇢  H2+ + SO4-2

  • Sulphuric Acid is a good oxidizing agent, as it oxidizes other substances by donating its oxygen atoms, in a chemical reaction. As shown below, it oxidizes carbon and sulphur.

2H2SO4 + C ⇢  2H2O + 2SO2 + CO2

2H2SO4 + S ⇢  2H2O + 3SO2 

  • Sulfuric acid reacts vigorously with water in a highly exothermic reaction (i.e., releases heat).
  • Sulphuric Acid is a dibasic acid and releases two hydrogen ions per molecule.
  • Sulphuric Acid has hygroscopic properties, which implies that H2SO4 can draw and control moisture from its surroundings. This effect makes it a good dehydrating agent.
  • It is less volatile. This is why it contributes to preparing more volatile acids from their complementary salts.

Structure of Sulphuric Acid

Two oxygen atoms form double bonds with the Sulphur atom, while two hydroxyl groups (OH) form single bonds with the Sulphur atom. Due to its ability to release two protons, it is a diprotic acid. As shown below, the molecule has a tetrahedral structure and is covalent.

Structure of Sulfuric Acid


Preparation of Sulfuric Acid

Sulfuric Acid is generally prepared and manufactured by the following two methods, which are widely used.

  1. Contact Process
  2. Lead Chamber Process

Contact Process for manufacturing of Sulfuric Acid

The Contact Process comprises three phases in the production of sulphuric acid:

  • Preparation of Sulphur dioxide by burning sulphur or sulphide ores in the air.

S (s) + O2 (g)  →  SO2 (g)

  • Reaction between sulphur dioxide with oxygen in the presence of V2O5 catalyst to produce Sulphur trioxide (SO3) as,

2SO2 (g) + O2 (g)  →  2SO3 (g)

SO3 + H2SO4 (Oleum)  →  H2S2O7

H2S2O7 (l) + H2O (l)  →  2H2SO4 (Sulfuric Acid)

The sulphuric acid obtained by the Contact process is 96–98% pure.

Lead Chamber Process

One of the most popular manufacturing processes is the lead Chamber method. It produces around 50 to 60 B-grade acids. Wet SO2 in the presence of nitrogenous oxides is used in this procedure (dynamic impetus). As a result, it undergoes oxidation with airborne oxygen to produce sulphur trioxide. This reaction is stated as,

2SO2 +  O2  →  2SO3

Then, water and sulphur trioxide are allowed to interact, resulting in H2SO4. This reaction is stated as,

SO3  +  H2O  →  H2SO4

Molecular Mass of Sulphuric Acid

Sulphuric acid has the chemical formula H2SO4. According to this formula, one molecule of sulphuric acid (H2SO4) comprises 2 moles of hydrogen, 1 mole of sulfur, and 4 moles of oxygen atoms. As a result, the molecular mass of H2SO4 will be equal to the sum of the masses of two moles of hydrogen, one mole of sulfur, and four moles of oxygen. Because hydrogen has an atomic mass of 1u, sulfur has an atomic mass of 32u, and oxygen has an atomic mass of 16u, the molecular mass of sulphuric acid may be computed as follows:

The molecular mass of H2SO4 = Mass of 2 moles of hydrogen atoms + Mass of 1 mole of sulphur + Mass of 4 moles of oxygen atoms

= 2 × 1 + 32 + 4 × 16

= 2 + 32 + 64

= 98 u

Thus, the molecular mass of sulphuric acid is 98u and the molecular weight of sulphuric acid is 98 g/mol.

Reactions of Sulfuric Acid

  • Dissociation- When pure water-free sulphuric acid is cooked, sulfur trioxide and water are formed.

H2SO4 → SO3 + H2O

  • Acidic Character of Sulphuric Acid- It’s a common dibasic acid that turns blue litmus crimson when exposed to it. It divides into two groups of salts.

NaOH + H2SO4 → NaHSO4 + H2O

2NaOH + H2SO4 → Na2SO4 + 2H2O

  • Sulphonating Action of Sulphuric Acid- Concentrated sulphuric acid combines with a variety of organic molecules, such as benzene, toluene, and others, to form sulphonic acids, as an example.

C6H6 + H2SO4 → C6H5SO3H + H2O

  • Precipitation Reactions with Sulphuric Acid- It creates insoluble sulfates that precipitate when handled with aqueous solutions of barium, lead, and other salts, for example.

H2SO4 + BaCl2 → BaSO4↓ + 2HCl

  • Reaction with Sulphur Trioxide- Oleum, commonly known as fuming sulphuric acid, is formed when it dissolves sulfur trioxide.

H2SO4 + SO3 → H2S2O7

Uses of Sulfuric Acid

Sulfuric acid is known as one of the most essential reagents, and it has several industrial uses. Several instances include:

  • Fertilizers such as ammonium sulfate, lime superphosphate, and others are made in this way.
  • In the production of colors, explosives, and pharmaceuticals.
  • H2SO is used in the production of acids such as HCl and HNO3.
  • In the production of pigments, paints, and polymers, for example.
  • In the paper and textile industries, for example.
  • Nitrocellulose is used in the production of goods.
  • Applications in metallurgy (Example: Cleaning metals before enameling, electroplating, and galvanizing).
  • In the leather business.
  • In storage compartments.
  • In the oil and gas sector.
  • In the detergent business.
  • It works as a dehydrator.
  • As a reagent in the laboratory.

FAQs on Sulfuric Acid

Question 1: What are the uses of sulphuric acid?


Fertilizers, dyestuffs, explosives, and pharmaceuticals are all made with sulphuric acid. It is also used to make acids such as HCl and HNO3. It’s frequently utilised in the metallurgical industry (Example: Cleaning metals before enamelling, electroplating and galvanising).

Question 2: Why is Sulphuric acid called the king of chemicals?


Sulphuric acid, sometimes known as the “king of chemicals,” is one of the most significant substances. It’s also known as vitriol oil since it used to be made from green vitriol back in the day. It is very corrosive and more reactive than other acids. As a result, it has a wide range of uses, including usage in laboratories, batteries, detergents, and the manufacture of numerous medications.

Question 3: What will happen when Sulphuric Acid reacts with aqueous solutions of the salts of barium?


It generates insoluble sulphates that precipitate when handled with aqueous solutions of barium salts.

H2SO4 + BaCl2 → BaSO4↓ + 2HCl

Question 4: What will happen when Sulphuric Acid reacts with Sulphur Trioxide?


Sulphuric acid dissolves sulphur trioxide to generate oleum, often known as fuming sulphuric acid.

H2SO4 + SO3 → H2S2O7

Question 5: What is the structure of sulphuric acid?


In sulphuric acid, two hydrogen atoms are firmly bonded to two oxygen atoms, resulting in two-OH groups. The molecule is covalent and has a tetrahedral structure.

structure of sulphuric acid


Question 6: Which acid is the strongest in the world?


Fluoroantimonic acid is a superacid mixture of Antimony Pentafluoride and Hydrofluoric Acid, which is the strongest in the world.

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