Sulphuric Acid H2SO4 - Physical Properties, Reactions with Salts, Metals, and More

Sulphuric Acid H₂SO₄

Sulfuric acid or sulphuric acid also referred to as oil of vitriol, is a mineral acid made up of the elements sulphur, oxygen and hydrogen, with molecular formula H₂SO₄.

Sulphuric acid was first prepared by a Muslim scientist Jabir bin Hayyan in the 8th century.

In Europe, in the 14th and 15th centuries, its preparation on the business level was begun due to the awareness of its properties and usages.

Small quantities of H₂SO₄ are found in the waters of some springs and rivers.

Table of Contents Hide

1) Manufacture of Sulphuric Acid
2) Contact Process
3) Principle
4) Properties of Sulphuric Acid
5) Sulphuric Acid as an Acid
6) Sulphuric Acid as a Dehydrating Agent
7) Sulphuric Acid as an Oxidizing Agent
8) Uses of Sulphuric Acid
9) MCQs with Answers – Sulphuric Acid (H2SO4)
10) Frequently Asked Questions (FAQs)
11) Summary – Sulphuric Acid H2SO4
12) You may also like to learn:

Manufacture of Sulphuric Acid

Sulphuric acid is being manufactured frequently by the contact process.

Contact Process

This approach was developed by Knietsch in Germany. It includes the catalytic mix of sulphur and oxygen to form SO₂ which is then dissolved in water to form H₂SO₄.

Principle

SO₂ acquired by burning sulphur or iron pyrites is oxidized to SO₃ in the presence of V₂O₅ which functions as a catalyst. The very best yield of SO₃can be acquired by using an excess of oxygen or air and keeping the temperature in between 400-500 ° C. SO₃ formed is absorbed in concentrated H₂SO₄and “Oleum” (H₂S₂O₇) formed can be converted to sulphuric acid of any strength by mixing sufficient amounts of water.

The process is completed in the series provided listed below.

a.Sulphur Burners

Sulphur or iron pyrites are burnt more than air to produce SO₂.

b.Purifying Unit

SO₂ is cleansed from impurities like dust and arsenic oxide, to avoid poisoning of the catalyst. The cleansing system consists of the following parts.

(i) Dust cleaner

Steam is injected to get rid of dust particles from the gases.

(ii) Cooling Pipes

The gases are passed through lead pipes to cool them to 100 ° C.

(iii) Scrubbers

The cooled gases are washed by a spray of water, as SO₂ is not soluble in water at high temperatures.

(iv) Drying Tower

The moisture of gases is gotten rid of by concentrated H2SO4 trickling down through the coke filled in this tower.

(v) Arsenic Purifier

Arsenic oxide is then eliminated by passing the gases through a chamber provided with racks loaded with freshly prepared ferric hydroxide.

(vi) Testing box

In this box, a beam of light is introduced which indicates the presence or absence of solid particles. If present the gases are sent back for further purification filtration.

c.Contact Tower

Preheated gases at 400-500 ° C are passed through vertical iron columns packed with the catalyst V₂O₅. Here SO₂ is oxidized to SO₃.

The reaction is extremely exothermic so no heating is needed once the reaction is started.

d.Absorption Unit

The SO₃ acquired from the contact tower is dissolved in 98% H₂SO₄ to form pyrosulphuric acid (oleum), H₂S₂O₇. It can be diluted with water to get any required concentration of sulphuric acid.

Properties of Sulphuric Acid

Physical Properties

Pure sulphuric acid is a colourless oily liquid without a smell.
Its specific gravity is 1.834 at 18 ° C.
It freezes at 10.5 ° C.
Its boiling point is 338 ° C.
It dissolves in water liberating a lot of heat which raises the temperature of the mixture as much as 120 ° C. H₂SO₄ should always be poured in water in a thin stream to avoid any mishap.
Pure acid is a nonconductor of electricity but the addition of a little water makes it a great conductor.
It is incredibly corrosive to skin and causes really severe burns to all the tissues.

It is stable at ordinary temperature level but on strong heating, it dissociates into SO₃ and H₂O.

Further Reading: Hydrogen - Occurrence, Properties, Uses & Isotopes of Hydrogen

It is a strong acid. In an aqueous solution, it entirely ionizes to give hydrogen, hydrogen sulphate and sulphate ions. The dissociation takes place in two steps.

Sulphuric Acid as an Acid

(i) Reactions with alkalies

(ii) Reactions with carbonates and hydrogen carbonates

(iii) Reactions with salts

(iv) Reactions with metals

Cold dilute acid reacts with almost all metals to produce hydrogen gas and sulphate salts.

Cold concentratedH₂SO₄does do not react with most of the metals like Cu, Ag, Hg, Pb, Au.

With specific metals hot concentrated sulphuric acid provides metal sulphates, water and SO₂.

Sulphuric Acid as a Dehydrating Agent

H₂SO₄ has a great affinity for water, so it acts as a dehydrating agent and removes water from different compounds.

For instance:

With formic acid, CO is formed.

With ethyl alcohol, it forms ethylene.

With wood, paper, sugar and starch it forms carbon and water.

Sulphuric Acid as an Oxidizing Agent

H₂SO₄ acts as a strong oxidizing agent.

It oxidizes C and S giving CO₂ and SO₂, respectively.

H₂S is oxidized to S.

Reactions of H₂SO₄with HBr and HI produces bromine and iodine respectively.

Uses of Sulphuric Acid

It is used

in the manufacture of fertilizers like ammonium sulphate and calcium superphosphate.
in the refining of petroleum to get rid of nitrogen and sulphur substances.
in the manufacture of HCl, H₃PO₄, HNO₃ and sulphates.
in the manufacture of numerous chemicals, dyes, drugs, plastics, disinfectants, paints, explosives, artificial fibres, etc.
in electrical batteries and storage cells.
as a dehydrating agent for drying gases.
as a laboratory reagent.
in textile, iron, steel, leather and paper markets.

MCQs with Answers – Sulphuric Acid (H2SO4)

1. What is the molecular formula of sulphuric acid?
- a. SO2
- b. H2SO4
- c. H2S
- d. H2O
- Answer: b
2. Who first prepared sulphuric acid in the 8th century?
- a. Robert Boyle
- b. Antoine Lavoisier
- c. Jabir bin Hayyan
- d. Humphry Davy
- Answer: c
3. Which process is commonly used for the manufacture of sulphuric acid?
- a. Haber Process
- b. Solvay Process
- c. Contact Process
- d. Ostwald Process
- Answer: c
4. What is the catalyst used in the Contact Process for the production of sulphuric acid?
- a. Fe2O3
- b. V2O5
- c. Ni
- d. Pt
- Answer: b
5. At what temperature is the Contact Process typically carried out?
- a. 100-200 °C
- b. 200-300 °C
- c. 300-400 °C
- d. 400-500 °C
- Answer: c
6. Which unit in the Contact Process is responsible for oxidizing SO2 to SO3?
- a. Sulphur Burners
- b. Purifying Unit
- c. Contact Tower
- d. Absorption Unit
- Answer: c
7. What is the specific gravity of pure sulphuric acid at 18 °C?
- a. 1.000
- b. 1.220
- c. 1.834
- d. 2.000
- Answer: c
8. What is the freezing point of pure sulphuric acid?
- a. -10.5 °C
- b. 0 °C
- c. 10.5 °C
- d. 20 °C
- Answer: a
9. How does sulphuric acid behave as an oxidizing agent?
- a. It reduces C to CO2
- b. It oxidizes H2S to S
- c. It reacts with metals to form salts
- d. It reacts with alkalies to form salts
- Answer: b
10. In the Contact Process, what is the final product formed in the Absorption Unit?
- a. Sulphuric Acid
- b. Oleum
- c. Sulphur Dioxide
- d. Pyrosulphuric Acid
- Answer: b
11. What is the primary use of sulphuric acid in the manufacturing industry?
- a. Food Preservation
- b. Cleaning Agent
- c. Fertilizer Production
- d. Medicinal Purposes
- Answer: c
12. What does sulphuric acid form when it reacts with wood, paper, sugar, and starch?
- a. Ethylene
- b. Carbon and Water
- c. Hydrogen Gas
- d. CO2 and SO2
- Answer: b
13. What happens to sulphuric acid when strongly heated?
- a. It freezes
- b. It dissociates into SO3 and H2O
- c. It turns yellow
- d. It becomes a solid
- Answer: b
14. What is the primary role of the Sulphur Burners in the Contact Process?
- a. Oxidize SO2 to SO3
- b. Purify SO2 from impurities
- c. Absorb SO3 in concentrated H2SO4
- d. Generate SO2 by burning sulphur
- Answer: d
15. What is the colour of pure sulphuric acid?
- a. Yellow
- b. Blue
- c. Colourless
- d. Red
- Answer: c
16. What is the primary role of the Dust Cleaner in the Purifying Unit?
- a. Remove arsenic oxide
- b. Eliminate dust particles from gases
- c. Cool the gases
- d. Remove moisture from gases
- Answer: b
17. How does sulphuric acid act as a dehydrating agent with ethyl alcohol?
- a. Forms CO
- b. Forms ethylene
- c. Forms carbon and water
- d. Forms CO2
- Answer: b
18. What is the role of the Arsenic Purifier in the Purifying Unit?
- a. Remove arsenic oxide
- b. Eliminate dust particles from gases
- c. Cool the gases
- d. Remove moisture from gases
- Answer: a
19. What does sulphuric acid dissociate into at ordinary temperatures?
- a. H2O and SO3
- b. H2 and SO4
- c. SO2 and H2
- d. SO3 and H2O
- Answer: d
20. What is the primary role of the Cooling Pipes in the Purifying Unit?
- a. Remove arsenic oxide
- b. Eliminate dust particles from gases
- c. Cool the gases
- d. Remove moisture from gases
- Answer: c
21. In the Sulphuric Acid Emission Tower, what is used as a catalyst to oxidize SO2 to SO3?
- a. Fe2O3
- b. V2O5
- c. Ni
- d. Pt
- Answer: b

Further Reading: Chromatography: Paper Chromatography & Uses of Chromatography

Frequently Asked Questions (FAQs)

What is the molecular formula of sulphuric acid?
- Sulphuric acid has the molecular formula H₂SO₄.
Who first prepared sulphuric acid, and when?
- Sulphuric acid was first prepared by the Muslim scientist Jabir bin Hayyan in the 8th century.
How is sulphuric acid commonly manufactured?
- Sulphuric acid is commonly manufactured by the contact process.
What is the Contact Process, and who developed it?
- The Contact Process, developed by Knietsch in Germany, involves the catalytic mix of sulphur and oxygen to form SO2, which is then dissolved in water to form H2SO4.
What is the principle catalyst used in the Contact Process?
- The principle catalyst used in the Contact Process is V2O5.
Describe the series of units involved in the Contact Process.
- The series includes Sulphur Burners, Purifying Unit, Contact Tower, and Absorption Unit.
What is the role of Sulphur Burners in the Contact Process?
- Sulphur or iron pyrites are burnt in excess of air in Sulphur Burners to produce SO2.
Why is the Purifying Unit essential in the Contact Process?
- The Purifying Unit cleanses SO2 from impurities like dust and arsenic oxide, preventing catalyst poisoning.
What is the specific gravity of pure sulphuric acid at 18 °C?
- The specific gravity of pure sulphuric acid at 18 °C is 1.834.
Is sulphuric acid a good conductor of electricity?
- Pure acid is a nonconductor of electricity, but the addition of a little water makes it a good conductor.
How does sulphuric acid act as a dehydrating agent?
- Sulphuric acid acts as a dehydrating agent by removing water from different compounds.
What happens when sulphuric acid reacts with metals?
- Cold dilute acid reacts with almost all metals to produce hydrogen gas and sulphate salts.
What are the primary uses of sulphuric acid in the manufacturing industry?
- Sulphuric acid is used in the manufacture of fertilizers, refining petroleum, production of various chemicals, dyes, drugs, plastics, disinfectants, paints, explosives, artificial fibers, etc.
How does sulphuric acid behave as an oxidizing agent?
- Sulphuric acid acts as a strong oxidizing agent, oxidizing C and S to give CO2 and SO2, respectively.
What does sulphuric acid form when it reacts with wood, paper, sugar, and starch?
- Sulphuric acid reacts with wood, paper, sugar, and starch to form carbon and water.
Can you freeze pure sulphuric acid?
- Yes, pure sulphuric acid freezes at 10.5 °C.
What is the boiling point of pure sulphuric acid?
- The boiling point of pure sulphuric acid is 338 °C.
What is the main product formed in the Absorption Unit during the Contact Process?
- The main product formed in the Absorption Unit is pyrosulphuric acid (oleum), H2S2O7.
Is sulphuric acid stable at ordinary temperatures?
- Yes, sulphuric acid is stable at ordinary temperatures, but it dissociates into SO3 and H2O on strong heating.
How does sulphuric acid react with alkalies?
- Sulphuric acid reacts with alkalies to form salts.
What are the safety precautions when handling sulphuric acid?
- Sulphuric acid is corrosive and can cause severe burns. Always pour it into water in a thin stream to avoid accidents. Protective equipment should be worn when handling it.

Summary – Sulphuric Acid H2SO4

Sulphuric Acid (H2SO4) is a vital mineral acid composed of sulphur, oxygen, and hydrogen. Originally prepared by the 8th-century Muslim scientist Jabir bin Hayyan, its industrial production gained momentum in 14th and 15th-century Europe. This tutorial explores its properties, manufacturing through the Contact Process, and various applications.

Manufacture of Sulphuric Acid: The Contact Process, developed by Knietsch, involves catalytically mixing sulphur and oxygen to form SO2, oxidizing it to SO3 in the presence of V2O5 catalyst, and dissolving it in concentrated H2SO4. The process includes Sulphur Burners, Purifying Unit, Contact Tower, and Absorption Unit.

Properties of Sulphuric Acid:

Pure sulphuric acid is a colorless, oily liquid without smell.
Specific gravity: 1.834 at 18°C; Freezing point: 10.5°C; Boiling point: 338°C.
Highly corrosive, it dissolves in water liberating heat, and ionizes into hydrogen, hydrogen sulphate, and sulphate ions.

Sulphuric Acid’s Functions:

As an Acid: Reacts with alkalies, carbonates, hydrogen carbonates, salts, and metals.
Dehydrating Agent: Removes water from various compounds, forming CO, ethylene, carbon, and water.
Oxidizing Agent: Oxidizes carbon and sulphur, producing CO2, SO2, and oxidizing H2S to S.

Uses of Sulphuric Acid:

In fertilizers (ammonium sulphate, calcium superphosphate) manufacture.
In refining petroleum to eliminate nitrogen and sulphur compounds.
In the production of various chemicals, dyes, drugs, plastics, disinfectants, paints, explosives, and artificial fibers.
In electrical batteries, storage cells, and as a dehydrating agent for drying gases.
As a laboratory reagent and in textile, iron, steel, leather, and paper industries.

Conclusion: Sulphuric Acid plays a pivotal role in diverse industrial processes, showcasing its significance in chemistry, manufacturing, and various industrial applications. Understanding its properties and applications is crucial for safe and efficient handling in industrial and laboratory settings.