Preparations of H2SO4 and H2SO3, their Properties and Uses | Chemistry for JAMB PDF Download

Preparation, Properties, and Uses of Sulphur(IV) Oxide

Preparation:

Sulphur(IV) oxide, also known as sulphur dioxide (SO₂), can be prepared through various methods. The most common method involves burning sulphur in an excess of air or oxygen:

S(s) + O₂(g) → SO₂(g)

Properties:

• Sulphur(IV) oxide is a colorless gas with a pungent odor.
• It is soluble in water, forming sulphurous acid (H₂SO₃).
• It is a non-flammable gas.
• It is denser than air and can be collected by downward displacement of air.
• It can act as both a reducing and an oxidizing agent.

Uses:

• Sulphur(IV) oxide is used in the production of sulfuric acid.
• It is used as a preservative for dried fruits and vegetables.
• It is employed as a bleach in the paper and textile industries.
• It is used as a reducing agent in the metallurgical processes.
• It finds application in the preparation of sodium thiosulphate used in photography.

Reaction of SO₂ with Alkalis

When sulphur(IV) oxide reacts with alkalis (bases), it forms sulphites. The reaction can be represented by the following equation:
SO₂(g) + 2NaOH(aq) → Na₂SO₃(aq) + H₂O(l)
The resulting product is a sodium sulphite, and water is formed as a byproduct. This reaction is a neutralization reaction, where an acid (SO₂) reacts with a base (NaOH) to form a salt (Na₂SO₃) and water.

Trioxosulphate(IV) Acid and its Salts - the Effect of Acids on Salts of Trioxosulphate(IV)

Trioxosulphate(IV) acid, also known as sulphurous acid (H₂SO₃), is a weak acid that exists in aqueous solution. When acids are added to salts of trioxosulphate(IV), they react to form other salts and water. This reaction can be represented by the following equation:
Na₂SO₃(aq) + 2HCl(aq) → 2NaCl(aq) + H₂SO₃(aq)
In this reaction, sodium sulphite reacts with hydrochloric acid to produce sodium chloride and sulphurous acid. The sulphurous acid formed is unstable and readily decomposes to sulphur dioxide and water.

Tetraoxosulphate(VI) Acid: Commercial Preparation (Contact Process only), Properties as a Dilute Acid, an Oxidizing and a Dehydrating Agent, and Uses

Commercial Preparation (Contact Process):

Tetraoxosulphate(VI) acid, commonly known as sulphuric acid (H₂SO₄), is commercially prepared by the Contact Process. The process involves several steps:

• Oxidation of sulphur dioxide:
  2SO₂(g) + O₂(g) → 2SO₃(g)
• Absorption of sulphur trioxide in concentrated sulphuric acid:
  SO₃(g) + H₂SO₄(l) → H₂S₂O₇(l)
• Dilution of oleum (fuming sulphuric acid) with water:
  H₂S₂O₇(l) + H₂O(l) → 2H₂SO₄(l)

Properties as a Dilute Acid:

• Sulphuric acid is a colorless, odorless, and oily liquid.
• It is highly corrosive and can cause severe burns.
• It is a strong acid and dissociates completely in water.
• It has a high boiling point and is a non-volatile liquid.

Properties as an Oxidizing Agent:

• Sulphuric acid can act as an oxidizing agent, particularly at high concentrations.
• It can oxidize certain metals, such as iron, to form metal sulfates.
• It can oxidize non-metals, such as carbon, to carbon dioxide.

Properties as a Dehydrating Agent:

• Sulphuric acid is a powerful dehydrating agent due to its strong affinity for water.
• It can remove water from substances, such as sugar and paper, by reacting with the water molecules and forming stable compounds.

Uses:

• Sulphuric acid is widely used in the production of fertilizers, such as ammonium sulfate and superphosphate.
• It is used in the manufacturing of detergents, dyes, and pigments.
• It is employed in petroleum refining and the production of various chemicals.
• It is used in the production of explosives, such as nitroglycerin.
• It is utilized in the lead-acid battery industry.

Test for SO₂⁻⁴

The test for the sulfate ion (SO₂⁻⁴) involves adding a few drops of barium chloride solution (BaCl₂) to a test solution containing the sulfate ion. A white precipitate of barium sulfate (BaSO₄) is formed if the sulfate ion is present. The reaction can be represented by the following equation:
BaCl₂(aq) + SO₄^2-(aq) → BaSO₄(s) + 2Cl^-(aq)
The formation of a white precipitate confirms the presence of the sulfate ion in the test solution. The test is commonly used to identify sulfates in qualitative analysis.