Anhydrides

Rucete ✏ Chemistry In a Nutshell

1. What Is an Anhydride?

• An anhydride is a compound that forms an acid or base when water is added.
• The word literally means "without water".

2. Acidic Anhydrides

• These are non-metal oxides that form acids when they react with water.
• General reaction:
  Non-metal oxide + H₂O → Acid
• Example:
  SO₃ + H₂O → H₂SO₄
• SO₃ is an acidic anhydride because it forms sulfuric acid.

3. Basic Anhydrides

• These are metal oxides that form bases when reacted with water.
• General reaction:
  Metal oxide + H₂O → Base
• Example:
  CaO + H₂O → Ca(OH)₂
• CaO is a basic anhydride because it forms calcium hydroxide.

4. Amphoteric Substances

• Compounds that can act as either acids or bases, depending on the reacting partner.
• Common amphoteric hydroxides include:
  • Al(OH)₃
  • Be(OH)₂
  • Cr(OH)₃
  • Zn(OH)₂