What are examples of amphoteric substances?

Short Answer

Amphoteric substances are chemicals that can act as both acids and bases. Common examples include aluminum hydroxide (Al(OH)₃), zinc oxide (ZnO), lead(II) oxide (PbO), water (H₂O), and chromium hydroxide (Cr(OH)₃).

These substances react with acids to form salts and with bases to form complex ions, showing their dual behavior. They are widely used in laboratory, industrial, and environmental applications.

Detailed Explanation :

Definition of Amphoteric Substances

An amphoteric substance is a chemical compound that can behave as an acid or a base depending on the reaction conditions. In acidic environments, it reacts as a base, accepting protons. In basic environments, it reacts as an acid, donating protons.

This dual behavior makes them very versatile in chemical reactions.

  1. Metal Hydroxides
  1. Aluminum Hydroxide (Al(OH)₃)
    • Reacts with acids:

Acts as a base.

    • Reacts with bases:

Acts as an acid.

  1. Chromium Hydroxide (Cr(OH)₃)
    • Acts as a base with acids:
    • Acts as an acid with bases:

These hydroxides are sparingly soluble and widely used in industrial and analytical chemistry.

  1. Metal Oxides
  1. Zinc Oxide (ZnO)
    • Reacts with acids:

Base behavior.

    • Reacts with bases:

Acid behavior.

  1. Lead(II) Oxide (PbO)
    • Reacts with acids: forms lead salts.
    • Reacts with bases: forms complex salts, e.g., plumbate.

Metal oxides show amphoteric behavior due to hydroxyl groups formed in water.

  1. Water (H₂O)
  • Acts as a base with acids:
  • Acts as an acid with bases:

Water is an example of an amphoteric solvent, participating in acid-base reactions.

  1. Other Examples
  • Tin(II) Oxide (SnO)
  • Beryllium Hydroxide (Be(OH)₂)
  • Gallium Hydroxide (Ga(OH)₃)

All of these can react with both acids and bases, forming salts or complex ions.

  1. Applications of Amphoteric Substances
  1. Industrial Uses
    • Al(OH)₃ is used in water purification and antacids.
    • ZnO is used in paints, rubber, and cosmetics.
  2. Laboratory Reactions
    • Amphoteric compounds are used in titrations and precipitation reactions.
  3. Environmental Chemistry
    • Neutralizes acidic or basic wastes, buffering environmental systems.
  1. Summary
  • Amphoteric substances can act as both acids and bases.
  • Common examples include:
    1. Al(OH)₃
    2. ZnO
    3. PbO
    4. H₂O
    5. Cr(OH)₃
  • Their dual behavior is important in industrial, laboratory, and environmental applications.
Conclusion

Amphoteric substances are versatile chemicals that react with both acids and bases, forming salts and complex ions. Examples like aluminum hydroxide, zinc oxide, and water demonstrate this dual behavior. Understanding these examples is essential in predicting reactions, industrial processes, and environmental management, highlighting the importance of amphoteric substances in chemistry and daily life.