Sulphuric Acid

What is H2SO4?

Acids are those substances which release hydrogen or hydronium ions when dissolved in their solutions. Acids can also be defined as those substances which donate a proton. Sulphuric Acid is a strong mineral acid, which is represented by the chemical formula H2SO4. Sulphuric Acid is also known as the king of chemicals due to its immense uses in various industries, especially heavy industries. It is also called mattling acid and the oil of vitriol. In the eighteenth century, Sulphuric Acid was produced from green vitriol. The Sulphuric Acid thus developed has an oily look. So, it was then named as the oil of vitriol.

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H2SO4 Chemical Name

The chemical name of H2SO4 is hydrogen sulphate or di-hydrogen sulphate. It contains two atoms of hydrogen, one atom of sulphur, and four atoms of oxygen. It has an atomicity of seven.

Hydrogen sulphate is basically an ionic bond. The two ions participating in this bond are hydrogen ion (cation) and sulphate ion (anion). 

H2SO4 Structure

 The Sulphuric Acid structure can be described as follows: - 

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Properties of Sulphuric Acid 

  • Strong Acid: Completely dissociates into ions in its aqueous solution

  • Oxidising Agent: It tends to oxidise other substances in a reaction by donating its oxygen atoms. In the following reactions, it oxidises carbon and sulphur. 

2H2SO4 + C —-> 2H2O + 2SO2 + CO

2H2SO4 + S —-> 2H2O + 3SO2

  • Basicity: The basicity of an acid is the number of hydrogen ions it releases per molecule. Sulphuric Acid is a dibasic acid and releases two hydrogen ions per molecule.

  • Dehydrating Agent: Sulphuric Acid has hygroscopic properties, which means that it can attract and retain moisture from its environment. This property makes it a good dehydrating agent as it can take up and retain moisture from the surrounding and keep them dry. 

  • It has a high boiling point of 337 °C and a melting point of 10 °C. 

  • It turns blue litmus red and has a pH of around one or less.

  •  It is highly corrosive, making it dangerous to touch.

Molecular Weight of Sulphuric Acid 

The molecular mass is the mass of a substance, which is calculated by adding up the atomic mass of every atom present in one molecule of that substance. 

Sulphuric Acid contains three types of atoms, and we need to know the atomic mass of each of those. They are written below.

Atomic Mass of Hydrogen = 1 u

Atomic Mass of Sulphur = 32 u

Atomic Mass of Oxygen = 16 u

(Note: The above masses are a good approximation. We have excluded decimals for easier calculation)

We know that one molecule of hydrogen sulphate contains two atoms of hydrogen, one atom of sulphur, and four atoms of oxygen, the masses of which are given below.

Mass of 2 Hydrogen Atoms = 1 x 2 = 2 u

Mass of 1 Sulphur Atom = 32 u

Mass of 4 Oxygen Atoms = 16 x 4 = 64 u

The molecular mass of hydrogen sulphate is equal to the sum of all its atoms. 

Molecular Mass of Hydrogen Sulphate = 2 + 32 + 64

    = 98 u

Therefore, the molecular mass of Sulphuric Acid is 98 u. 

H2SO4 Molar Mass

Molar mass is the mass of one mole of a substance, measured in grams. One mole of a substance is defined as the Avogadro number (6.023 x 1023) molecules of that substance. 

Using the atomic mass of an individual atom and multiplying that by the conversion factor grams per mole (g/mol), you can determine the molar mass of that element.

The molar mass constant (our conversion factor) is defined as 0.001 kg/mol or 1 g/mole. Therefore, the Sulphuric Acid molar mass is 98 g/mole. 

Sulphuric Acid Uses

  1. It is used to make fertilisers. 

  2. It is used in the manufacture of steel and iron. It is also used as a cleaning agent in the industrial sector to erase rust from steel and iron.

  3. It is used in the chemical manufacturing industry. It is used to make phosphoric acid, hydrochloric acid, nitric acid, sulphate salts, synthetic detergents, dyes and pigments, explosives, medicines, and ammonium sulphate.

  4. It is used for oil processing.

  5. It functions as a catalyst in the reaction to convert cyclohexanone oxime to caprolactam. This reaction is used in the production of nylon.

  6. It is used to make batteries. In lead-acid batteries, Sulphuric Acid functions as an electrolyte. It can be used in storage batteries. Since it is present in a car battery, it is also known as car battery acid. 

Solved Examples

Question 1. Show the Reaction Between Sulphuric Acid and potassium.


Acids react with active metals to form metal salts and hydrogen gas. Potassium reacts with Sulphuric Acid to form potassium sulphate and hydrogen gas. 

H2SO4 + 2K————> K2SO4 + H2

FAQ (Frequently Asked Questions)

1. When Diluting Sulphuric Acid, Why Should We Put the Acid into the Water? Why not the Other Way Round? 

The reaction of acid and water leads to a decrease in the concentration of ions (H3O+) per unit volume. This process is referred to as dilution. This is a highly exothermic reaction. 

If we add the water into the acid, a highly concentrated solution of acid is formed first, which releases a tremendous amount of heat. This heat makes the acid bubble, and splash. This can cause severe burns and injury. It might even break the glass container in which it is held. 

If we add acid to the water, a much lesser amount of heat is generated at first, and this heat is also absorbed by the water, which is a much safer process of dilution. Hence, when diluting Sulphuric Acid, we should always put the acid into water, never the other way round. 

2. In the Event of an Acid Spill, How can we Neutralise Sulphuric Acid?

Add the baking soda directly to the acid spill. It can neutralise mild acids such as vinegar and even dangerous acids such as muriatic and Sulphuric Acid s. Drench the entire polluted surface with baking soda (sodium bicarbonate, NaHCO3) to neutralise the acid.