Short Answer

When an acid reacts with a base, they neutralize each other to form a salt and water. This reaction is called a neutralization reaction.

For example, hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water (H₂O):
HCl + NaOH → NaCl + H₂O
The reaction depends on the type of acid and base, and the products are usually a stable salt and water.

Detailed Explanation :

Reaction of Acid with Base

The reaction between an acid and a base is called a neutralization reaction. In this reaction, the hydrogen ions (H⁺) from the acid combine with the hydroxide ions (OH⁻) from the base to produce water (H₂O). The remaining ions from the acid and base combine to form a salt.

The general equation for a neutralization reaction is:

Acid + Base → Salt + Water

This reaction is exothermic, releasing heat, which is why many neutralization reactions feel warm.

Examples of Acid-Base Reactions

1. Hydrochloric acid + Sodium hydroxide
   HCl + NaOH → NaCl + H₂O

• Forms sodium chloride (common salt) and water.

1. Sulfuric acid + Potassium hydroxide
   H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O

• Forms potassium sulfate and water.

1. Nitric acid + Ammonium hydroxide
   HNO₃ + NH₄OH → NH₄NO₃ + H₂O

• Forms ammonium nitrate and water.

Mechanism of Neutralization

1. The acid dissociates in water to release H⁺ ions:
   HCl → H⁺ + Cl⁻
2. The base dissociates to release OH⁻ ions:
   NaOH → Na⁺ + OH⁻
3. H⁺ ions from the acid react with OH⁻ ions from the base to form water:
   H⁺ + OH⁻ → H₂O
4. The remaining ions (Na⁺ and Cl⁻) form a salt (NaCl) in solution.

This process removes the acidic and basic properties of the reactants.

Factors Affecting the Reaction

1. Strength of Acid and Base

• Strong acids and bases react faster and completely.
• Weak acids and bases react more slowly.

2. Concentration

• Higher concentration increases the rate of reaction and amount of heat released.

3. Temperature

• Higher temperatures increase the reaction rate and may help the neutralization process.

Observations During Neutralization

1. Heat Release – Reaction is usually exothermic.
2. No gas production (except when carbonate or bicarbonate salts are involved).
3. Solution becomes neutral – pH approaches 7 (depending on strength and concentration).

Neutralization reactions are predictable and important in chemical calculations.

Applications of Acid-Base Reactions

1. Preparation of Salts

• Salts like NaCl, K₂SO₄, and NH₄NO₃ are prepared via neutralization.

2. Medicine

• Antacids (like Mg(OH)₂, Al(OH)₃) neutralize excess stomach acid.

3. Agriculture

• Soil treatment: Lime (Ca(OH)₂) neutralizes acidic soils.

4. Industry

• Wastewater treatment: Neutralization of acidic or basic effluents.
• Manufacturing fertilizers, soaps, and chemicals relies on controlled acid-base reactions.

5. Laboratory Use

• Neutralization reactions are used to standardize solutions and calculate concentrations in titrations.

Types of Salts Formed

• From Strong Acid + Strong Base → Neutral salt (NaCl, K₂SO₄)
• From Strong Acid + Weak Base → Acidic salt (NH₄Cl)
• From Weak Acid + Strong Base → Basic salt (CH₃COONa)

This shows that the nature of the resulting solution depends on the strength of the reacting acid and base.

Conclusion

When an acid reacts with a base, a neutralization reaction occurs producing a salt and water. This reaction removes the acidic and basic properties of the reactants, often releasing heat. Neutralization reactions are widely used in salt preparation, medicine, agriculture, industry, and laboratory experiments. The type of salt formed depends on whether the acid and base are strong or weak, which also affects the pH of the resulting solution.