Acids, Bases, and Salts

The Essential Chemistry of Everyday Life

Acids, bases, and salts are among the most important substances in chemistry. They are not just abstract laboratory materials — they are everywhere in daily life. The sourness of lemons, the slipperiness of soap, the fizz in soda, the antacids we take for heartburn, and even the fertilizers used in agriculture all depend on the chemistry of acids, bases, and salts.

Understanding these substances is key to understanding chemical reactions, industrial processes, and even biological functions inside our bodies. This article explores their definitions, properties, reactions, examples, and applications in detail.

What are Acids, Bases, and Salts?

Acids

• Substances that release hydrogen ions (H⁺) in water.
• Taste sour (like lemon juice, vinegar).
• React with metals and bases.
• Example: Hydrochloric acid (HCl), Sulfuric acid (H₂SO₄).

Bases

• Substances that release hydroxide ions (OH⁻) or accept hydrogen ions.
• Taste bitter, feel slippery (like soap).
• Neutralize acids to form salts.
• Example: Sodium hydroxide (NaOH), Ammonium hydroxide (NH₄OH).

Salts

• Ionic compounds formed when an acid reacts with a base.
• Composed of a positive ion (cation) from the base and a negative ion (anion) from the acid.
• Example: Sodium chloride (NaCl), Potassium nitrate (KNO₃).

Historical Background

• Ancient Times: People knew about acidic and basic substances long before modern science (e.g., vinegar, ash, and lye).
• 17th Century: Robert Boyle distinguished acids and bases by taste and reactions.
• 19th Century: Svante Arrhenius defined acids as H⁺ producers and bases as OH⁻ producers.
• 20th Century: Brønsted–Lowry defined acids as proton donors and bases as proton acceptors.
• Lewis Theory: Defined acids as electron-pair acceptors and bases as electron-pair donors.

Properties of Acids

1. Taste: Sour (e.g., citric acid in oranges).
2. Conductivity: Conduct electricity in solution (electrolytes).
3. Reaction with Metals: Release hydrogen gas. Zn+2HCl→ZnCl2+H2Zn + 2HCl \rightarrow ZnCl₂ + H₂Zn+2HCl→ZnCl2​+H2​
4. Reaction with Carbonates: Produce carbon dioxide. CaCO3+2HCl→CaCl2+H2O+CO2CaCO₃ + 2HCl \rightarrow CaCl₂ + H₂O + CO₂CaCO3​+2HCl→CaCl2​+H2​O+CO2​
5. Change in Indicators: Turn blue litmus red.

Properties of Bases

1. Taste: Bitter.
2. Touch: Slippery or soapy feel.
3. Conductivity: Conduct electricity in solution.
4. Reaction with Acids: Neutralization. NaOH+HCl→NaCl+H2ONaOH + HCl \rightarrow NaCl + H₂ONaOH+HCl→NaCl+H2​O
5. Change in Indicators: Turn red litmus blue.

The pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14.

• pH < 7 → Acidic solution.
• pH = 7 → Neutral solution (pure water).
• pH > 7 → Basic solution.

Examples:

• Lemon juice: pH ~2.
• Vinegar: pH ~3.
• Baking soda: pH ~9.
• Soap: pH ~10–11.

Strong and Weak Acids/Bases

• Strong Acids: Completely ionize in water (HCl, H₂SO₄, HNO₃).
• Weak Acids: Partially ionize (CH₃COOH).
• Strong Bases: Completely ionize (NaOH, KOH).
• Weak Bases: Partially ionize (NH₄OH).

Neutralization Reaction

A reaction between an acid and a base forms salt and water. HCl+NaOH→NaCl+H2OHCl + NaOH \rightarrow NaCl + H₂OHCl+NaOH→NaCl+H2​O

Neutralization is important in many practical uses, from medicine (antacids neutralizing stomach acid) to agriculture (lime reducing soil acidity).

Preparation of Salts

Salts can be prepared in different ways:

1. Neutralization of Acid and Base
   Example: NaOH + HCl → NaCl + H₂O
2. Acid and Metal Reaction
   Example: Zn + H₂SO₄ → ZnSO₄ + H₂
3. Acid and Carbonate Reaction
   Example: CaCO₃ + HCl → CaCl₂ + H₂O + CO₂

Types of Salts

1. Normal Salts – completely neutralized acids (NaCl, K₂SO₄).
2. Acid Salts – formed when partial neutralization occurs (NaHSO₄).
3. Basic Salts – contain hydroxide ions (Mg(OH)Cl).
4. Double Salts – combination of two salts (alum).
5. Complex Salts – contain complex ions (K₄[Fe(CN)₆]).

Everyday Examples of Acids, Bases, and Salts

• Acids:
  • Citric acid (lemons, oranges).
  • Lactic acid (yogurt, sour milk).
  • Carbonic acid (carbonated drinks).
• Bases:
  • Sodium hydroxide (drain cleaner).
  • Ammonium hydroxide (cleaning agents).
  • Calcium hydroxide (lime water).
• Salts:
  • Sodium chloride (table salt).
  • Potassium nitrate (fertilizers, fireworks).
  • Sodium bicarbonate (baking soda).

Acids, Bases, and Salts in the Human Body

• Stomach Acid (HCl): Helps digest food.
• Blood pH: Maintained at ~7.4 using buffer systems.
• Salts in Nerves and Muscles: Sodium and potassium ions regulate nerve impulses and muscle contractions.
• Antacids: Neutralize excess stomach acid (e.g., magnesium hydroxide).

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Industrial Applications

Acids

• Sulfuric acid: used in fertilizers, car batteries.
• Nitric acid: used in explosives, dyes.
• Hydrochloric acid: used in cleaning, steel treatment.

Bases

• Sodium hydroxide: soap, paper, textiles.
• Calcium hydroxide: cement, bleaching.
• Ammonium hydroxide: fertilizers, cleaning.

Salts

• Sodium carbonate: glass manufacturing.
• Potassium nitrate: gunpowder.
• Calcium sulfate: plaster of Paris.

Environmental Role

1. Acid Rain
   • Formed when sulfur dioxide and nitrogen oxides dissolve in rainwater.
   • Harms plants, aquatic life, and buildings.
2. Soil Acidity
   • Corrected by adding lime (Ca(OH)₂).
3. Water Neutralization
   • pH adjustment necessary for safe drinking water.

Fun Facts

• Vitamin C is ascorbic acid.
• Ants inject formic acid when they bite.
• Soap works because it is a base that emulsifies oils.
• Neutral salts like NaCl are essential for life, but in excess can cause health problems.

Future Perspectives

• Green Chemistry: Developing eco-friendly acids and bases for industrial use.
• Biochemistry: Studying how acids, bases, and salts regulate metabolism.
• Space Chemistry: Investigating acidic and salty oceans on moons like Europa for signs of life.

Conclusion

Acids, bases, and salts are fundamental to chemistry and life. They explain why lemons taste sour, why soap feels slippery, why antacids relieve stomach discomfort, and why salts are vital for survival. From biology to industry, they play a central role in shaping the natural and technological world.

By studying acids, bases, and salts, we not only understand the chemistry of substances but also gain practical tools to improve health, environment, and technology.