Which one of the following is an amphoteric oxide? 

The correct answer is Al2O3.

Key PointsAmphoteric Oxides

• Amphoteric oxides are oxides that can act as both acids and bases. They can react with both acids and bases to produce salts and water.
• Aluminum oxide (Al2O3) is a classic example of an amphoteric oxide. It reacts with acids to form aluminum salts and water and with bases to form salts and water as well.
• For example, when Al2O3 reacts with hydrochloric acid (HCl), it forms aluminum chloride (AlCl₃) and water. When it reacts with sodium hydroxide (NaOH), it can form sodium aluminate (NaAlO₂) and water.
• This dual behavior is due to the electronic structure of the aluminum ion, which allows it to form covalent bonds with oxygen in acidic and basic environments.
• Magnesium oxide (MgO) and sodium oxide (Na₂O) are primarily basic oxides, while P₄O₁₀ is an acidic oxide, not demonstrate amphoteric properties.

Hence, the correct option is Al2O3.

Additional Information

• Basic oxides: These are oxides that react with acids to form salt and water. Examples include CaO (calcium oxide), which reacts with HCl to form calcium chloride and water.
• Acidic oxides: Oxides that react with bases to form salts and water. An example is SO₃ (sulfur trioxide), which reacts with NaOH to form sodium sulfate and water.
• Applications of Al₂O₃: Aluminum oxide has wide applications due to its physical and chemical properties. It is used as an abrasive in sandpapers, as a refractory material due to its high melting point, and in the production of aluminum metal.