What Are Salts?

A salt is a compound formed when the hydrogen ions (H⁺) of an acid are replaced by metal ions or ammonium ions.

Salts are usually produced during neutralisation reactions between acids and bases.

General reaction:

Acid + Base → Salt + Water

Example:

HCl + NaOH → NaCl + H₂O

In this reaction, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride (salt) and water.

Types of Salts

Salts can be classified based on the acid used to form them.

Chloride Salts

These salts are formed from hydrochloric acid (HCl).

Examples:

• Sodium chloride (NaCl)
• Copper(II) chloride (CuCl₂)

Sulfate Salts

These salts are formed from sulfuric acid (H₂SO₄).

Examples:

• Copper(II) sulfate (CuSO₄)
• Magnesium sulfate (MgSO₄)

Nitrate Salts

These salts are formed from nitric acid (HNO₃).

Examples:

• Potassium nitrate (KNO₃)
• Silver nitrate (AgNO₃)

Soluble and Insoluble Salts

Some salts dissolve in water, while others do not.

Soluble Salts

Salts that dissolve in water are called soluble salts.

Examples:

• Sodium salts
• Potassium salts
• Nitrate salts

These salts dissolve easily in water.

Insoluble Salts

Salts that do not dissolve in water are called insoluble salts.

Examples:

• Silver chloride
• Barium sulfate
• Lead(II) iodide

These salts form solid precipitates in solution.

Preparation of Soluble Salts

Soluble salts can be prepared using neutralisation reactions.

Common methods include:

Acid + Metal

Acid reacts with a metal to produce salt and hydrogen gas.

Example:

Zn + 2HCl → ZnCl₂ + H₂

Acid + Base

Acid reacts with a base to produce salt and water.

Example:

H₂SO₄ + CuO → CuSO₄ + H₂O

Acid + Carbonate

Acid reacts with a carbonate to produce salt, water, and carbon dioxide.

Example:

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Preparation of Insoluble Salts

Insoluble salts are prepared using the precipitation method.

In this method, two soluble solutions are mixed to produce an insoluble salt.

Example:

AgNO₃ + NaCl → AgCl + NaNO₃

Silver chloride forms as a white precipitate.

Importance of Salts

Salts are important in many fields such as:

• Agriculture (fertilizers)
• Food preservation
• Medicine and pharmaceuticals
• Industrial chemical production

Many important materials used in everyday life are salts.

Exam Tip (5070)

Students are often asked to:

• Define salts
• Identify types of salts
• Describe methods of salt preparation

Example exam question:

What type of salt is formed when sulfuric acid reacts with a base?

Answer:

A sulfate salt is formed.

Practice Question

What gas is produced when an acid reacts with a metal?

Answer

The gas produced is hydrogen (H₂).

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