Preparation, Types, Properties, and Uses of Salts | Chemistry for JAMB PDF Download

Introduction

Salts are fascinating chemical compounds that are formed through the reaction between acids and bases. When an acid reacts with a base, a salt is produced, exhibiting unique properties distinct from its constituent elements. Salts are ionic compounds composed of metal cations and organic or inorganic anions, making them soluble in water. This article explores the preparation methods, different types, properties, and diverse applications of salts.

Preparation of Salts

Salts can be prepared through various methods depending on the desired outcome. Here are some common approaches to salt synthesis:

1. Reaction of Metals with Acids

• Metal + Acid → Salt + H₂ (g)
• Example reactions:
  • HCl + Mg → MgCl₂ + H₂
  • H₂SO₄ + Zn → ZnSO₄ + H₂
  • CH₃COOH + Na → CH₃COONa + H₂

2. Reaction of Acids with Bases (Neutralization Reaction)

• Acid + Base → Salt + H₂O
• Example reactions:
  • 2HCl + Mg(OH)₂ → MgCl₂ + 2H₂O
  • H₂SO₄ + NaOH → Na₂SO₄ + H₂O

3. Reaction of Acids with Carbonates/Bicarbonates

• Acid + Carbonates/Bicarbonates → Salt + CO₂ + H₂O
• Example reactions:
  • 2HCl + MgCO₃ → MgCl₂ + CO₂ + H₂O
  • HCl + NaHCO₃ → NaCl + CO₂ + H₂O

4. Laboratory Synthesis of Salts

Salts can be synthesized in the laboratory using various methods. The process involves the step-by-step preparation of soluble or insoluble salts.

Naming Salts in Chemistry

Initially, salts were named based on their properties and uses, but the International Union of Pure and Applied Chemistry (IUPAC) introduced a globally accepted naming system. According to this system, salts are named by stating the cation first, followed by the anion. The charge or oxidation state of the cation is indicated in braces using Roman numerals. The table below provides examples of common salts, including their trade names and IUPAC names.

Types of Salts

Salts can be classified into various types based on their nature and composition. The following categories are commonly observed:

1. Acidic Salts

• These salts exhibit acidity due to the presence of acidic ions such as ammonium (NH₄⁺). They can donate a proton in a chemical reaction.
• Example: NH₄⁺ + H₂O → NH₃ + H₃O⁺

2. Basic Salts

• Basic salts contain ions that act as bases and accept protons in a chemical reaction. They exhibit basicity when dissolved in water.
• Example: NaCN → Na+ + CN^–; CN^– + H₂O → HCN + OH^–

3. Neutral Salts

• Neutral salts do not produce hydronium ions (H₃O⁺) or hydroxyl ions (OH^–) upon hydrolysis. They remain unreactive in water.
• Example: NaCl → Na⁺ + Cl^–; Cl^– + H₂O → no reaction

4. Double Salts

• Double salts contain more than one cation and occur naturally. They are found in the Earth's mantle and have unique compositions.
• Example: Mohr’s salt - (NH₄)₂Fe(SO₄)₂.6H₂O, Tutton’s salt - K₂Cd(SO₄)₂.6H₂O

5. Complex Salts

• Complex salts, also known as coordination compounds, contain transition metal cations surrounded by anions and ligands. They exhibit varying valencies.
• Example: Various coordination compounds with transition metals.

Properties of Salts

Salts possess distinct properties that make them noteworthy in chemistry. Some key properties include:

1. Solubility

• Salts are generally soluble in water due to their ionic nature. However, the solubility may vary, and sparingly soluble salts are characterized by their solubility product (Ksp).

2. Brittleness

• Salts are brittle and have a crystalline structure. When subjected to pressure, the layers displace, causing opposite charges to align, leading to crystal breakage.

3. High Melting and Boiling Points

• Salts form giant ionic lattices, resulting in high melting and boiling points. The strong electrostatic attractions between ions require significant energy to break the bonds.

4. Conductivity

• Salts exhibit conductivity in molten and aqueous states due to the presence of mobile ions and electrons that can carry an electric current.

Applications of Salts

Salts find numerous applications across various industries and everyday life. Some notable uses include:

1. Hot and Cold Packs

• Salts with endothermic or exothermic dissolution reactions are utilized in hot and cold packs to provide therapeutic effects and pain relief.

2. Clearing of Ice on Roadways

• Salt, such as sodium chloride, is commonly used to melt ice on roadways during winter. It lowers the melting point of ice, facilitating ice removal.

3. Food Flavor and Preservation

• Salts are essential for enhancing the taste of food and providing necessary nutrients. They have been used since ancient times for food preservation.

4. Tanning and Dyeing

• Salts play a crucial role in processes like mineral and leather tanning, as well as dyeing textiles. They aid in penetration and fixation of dyes.

5. Bleaching and Soap Production

• Salts, such as those derived from hydrochloric acid and hypochlorous acid, are used in bleaching applications. Salts also serve as intermediates in the production of soaps.

6. Pottery and Waterproofing

• Salts are utilized in the production of salt-glazed ware and clay surfaces, which can provide waterproofing properties.

7. Chlorine Production

• Salts are an affordable and easily accessible source of chlorine, making them valuable for various industrial processes.

Conclusion

Salts are versatile compounds that exhibit diverse properties and find applications in numerous fields. Understanding the preparation methods, types, and properties of salts enables scientists and industries to harness their potential in various chemical processes. From everyday uses like food flavoring and preservation to industrial applications such as dyeing and chlorine production, salts continue to play a vital role in our lives.