Sulphuric Acid

About Sulphuric Acid

Sulphuric acid, H₂SO₄ is an odorless, colorless, oily liquid that is extremely corrosive It was at first called Oil of Vitriol.

• It occurs in both combined and free state.

• It is framed close to the sulfide beds.

• In the joined frame, it happens as metallic sulfates (salts in minerals).

Fig. 1: A molecule of sulphuric acid

Fig. 2: Structure of sulfuric acid

Manufacture of Sulphuric Acid

Commercially, Sulphuric Acid can be prepared by two techniques that are as follows:

• Lead chamber process

• Contact process
   

Contact Process

The contact process includes three steps:

Step – I: 
Production of Sulphur Dioxide: 
This can be made by smoldering sulfur or sulfide ores, for example, iron pyrites in abundance of air.

 S (Sulphur) + O₂ (Oxygen) + Δ (Heating)  →  SO₂ (Sulphur dioxide)
 4FeS (Iron pyrites) + 7O₂ (Oxygen) + Δ (heating) →  2Fe₂O₃ (Ferric Oxide) + 4SO₂(Sulphur dioxide)

Step -II:

Formation of Sulphur Trioxide:

Sulphur dioxide is oxidized to sulphur trioxide with atmospheric oxygen within the sight of V₂O₅ as a catalyst.

2SO₂ (Sulphur dioxide) + O2 (Oxygen) + V₂O₅ (Catalyst) → SO₃ (Sulphurtriioxide)

Step -III

Conversion of Sulphur Trioxide into Sulphuric Acid:
The sulfur trioxide shaped in the second step is broken up in 98% sulphuric acid to give pyrosulphuric acid or oleum. Oleum is then diluted or weakened with water to give sulphuric acid of the concentration that is required.

 SO₃ (Sulphur trioxide) +  H₂SO₄ (Sulphuric acid-98%)  →    H₂S₂O₇ (Pyrosulphuric acid -Oleum)
 H₂S₂O₇ (Pyrosulphuric acid -Oleum) +  H₂O (Dilution )  →   2H₂SO₄(Sulphuric acid)

Fig. 3: A schematic diagram of a contact-process sulfuric acid converter

Fig. 4: Reactions and steps involved in the Contact Process

Lead Chamber Process

Lead Chamber process is one of the sulphuric acid manufacturing strategies which give just around 50-60 B grade acids. The fundamental standard of the procedure is that the wet SO₂ (Sulfur Dioxide) in the nearness of nitrogenous oxides (dynamic impetus) is oxidized to sulfur trioxide with the oxygen exhibit in air. Sulfur trioxide is made to react with water to create sulphuric acid. The reactions would resemble beneath:

• 2SO₂ + O₂ → 2SO₃

• SO₃ + H₂O → H₂SO_4​

Fig. 5: Lead chamber process
 

Physical Properties of Sulphuric Acid

• Sulphuric acid is a thick, colourless, oily fluid with a specific gravity of 1.84 at 298 K.

• The boiling point is 611 K. The high boiling point and thick nature is because of hydrogen bonding.

• Concentrated sulphuric acid has a strong water affinity. A lot of heat is created when the acid is blended with water.

• The acid is constantly diluted by adding it to water gradually with steady blending.

Remember - Never add water to Sulphuric Acid.

Fig. 6: Physical properties of Sulphuric Acid

Chemical Properties of Sulphuric Acid

Fig. 7: Chemical properties of Sulphuric Acid

Sulphuric Acid is a very strong dibasic acid. It ionizes in two stages in aqueous solution:

Step 1:
           H₂SO₄(aq) + H₂O(I)  →  H₃O⁺(aq) + HSO₄^-(aq);
           K_a1 = very large (K_a1 > 10)

Step 2:
           HSO₄(aq) + H₂O(I) →  H₃O⁺(aq) + SO₄^2-(aq);
           Ka₂ = 1.2 x 10^-2

• The acid neutralizes alkalis and structures two arrangement of salts bisulphates and sulfates.

Example:

Concentrated sulphuric acid reacts with sodium hydroxide and structures sodium bisulphate and sodium sulfate.

H₂SO₄ (Conc.Sulphuric acid) + 2NaOH (Sodium hydroxide)→  2NaHSO₄ (Sodium bisulphate) + H₂O (Water)
H₂SO₄ (Conc.Sulphuric acid)  + 2NaOH (Sodium hydroxide) →  Na₂SO₄ (Sodium sulphate) + 2H₂O (Water)

• Sulphuric acid is utilized as a part of the preparation of more volatile acids from their comparing salts as it is less volatile.
• Concentrated Sulphuric acid liberates hydrogen chloride from sodium chloride and hydrogen fluoride from calcium fluoride.

CaF₂ (Calcium fluoride)+ H₂SO₄ (Conc. Sulphuric acid) →  CaSO₄(Calcium sulphate)  +  2HF (Hydrogen floride)

• Concentrated Sulphuric acid is an intense dehydrating agent. This property is utilized as a part of drying many wet gasses that don't react with the acid.
• Sulphuric acid additionally expels water from natural mixes like starches.

Example:

• It burns glucose, sugar, and starch to carbon.

C₁₂H₂₂O₁₁(Cane sugar) + (H₂SO₄)  →  12C (Carbon)  +  11H₂O (Water)

• Hot concentrated Sulphuric acid is a decent oxidizing agent. It oxidizes both nonmetals as well as metals and itself gets reduced to sulfur dioxide.

Example of Sulphuric Acid

Hot concentrated sulphuric acid oxidizes copper to copper sulfate. Similarly, it oxidizes non-metallic carbon to carbon dioxide.

Cu (Copper) + 2H₂SO₄ (Hot suphuric acid) → CuSO₄ (Copper sulphate) + SO₂ (Sulphur dioxide) + H₂O (Water)
C (Carbon)  +  2H₂SO₄ (Hot suphuric acid)  →   CO₂ (Carbon dioxide) +  2SO₂ (Sulphur dioxide) + 2H₂O (Water)

• Sulphuric acid is utilized as a part of the preparation of more volatile acids from their comparing salts as it is less volatile.

Example:
Concentrated sulphuric acid liberates hydrogen chloride from sodium chloride and hydrogen fluoride from calcium fluoride.

CaF₂ (Calcium fluoride)+ H₂SO₄ (Conc. Sulphuric acid) →

 CaSO₄ (Calcium sulphate)  +  2HF (Hydrogen floride)

• Concentrated sulphuric acid is an intense dehydrating agent. This property is utilized as a part of drying many wet gasses that don't react with the acid.
• Sulphuric acid additionally expels water from natural mixes like starches.

Example:

• It burns glucose, sugar, and starch to carbon.

C₁₂H₂₂O₁₁ (Cane sugar) + (H₂SO₄) →  12C (Carbon)  +  11H₂O (Water)

• Hot concentrated sulphuric acid is a decent oxidizing agent. It oxidizes both nonmetals as well as metals and itself gets reduced to sulfur dioxide.

Example:

Hot concentrated sulphuric acid oxidizes copper to copper sulfate .Similarly, it oxidizes non-metallic carbon to carbon dioxide.

Cu (Copper) + 2H₂SO₄ (Hot suphuric acid) → CuSO₄ (Copper sulphate) + SO₂ (Sulphur dioxide) + H₂O (Water)
C (Carbon)  +  2H₂SO₄ (Hot suphuric acid)  →   CO₂ (Carbon dioxide) +  2SO₂ (Sulphur dioxide) + 2H₂O (Water)

Uses of Sulphuric Acid

Sulphuric acid, on account of its wide applications, is alluded as the King of Chemicals.

It is utilized as a part in the preparation of:

• Fertilisers like ammonium sulfate and superphosphate

• Dyes, shades, and paints

• Explosives, for example, TNT

• Other imperative chemicals like hydrochloric acid, phosphoric acid, nitric acid, and sodium carbonate

• It is utilized as a part of the refining of petroleum

• As a pickling agent

• As a laboratory agent, and an oxidizing and dehydrating agent

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Sulphuric Acid