An example of an amphoteric oxide is

Analysis

The question asks for an example of an amphoteric oxide. To solve this, we need to understand the chemical nature of oxides based on their position in the periodic table and their reactivity with acids and bases.

Concept Explanation

An amphoteric oxide is a metal oxide that exhibits both acidic and basic properties. This means it can react with an acid to form a salt and water, and it can also react with a base to form a salt and water.

• Basic Oxides: Usually formed by metals (e.g., K$_2$O, CuO). They react with acids but not with bases.
• Acidic Oxides: Usually formed by non-metals (e.g., P$_4$O$_{10}$, SO$_2$). They react with bases but not with acids.
• Amphoteric Oxides: These are "middle-ground" oxides. The most common examples you should memorize for your exams are Aluminium oxide (Al$_2$O$_3$), Zinc oxide (ZnO), and Lead(II) oxide (PbO).

Step-by-Step Solution

1. Evaluate Option A (P$_4$O$_{10}$): Phosphorus is a non-metal. Its oxide is acidic (it reacts with water to form phosphoric acid).
2. Evaluate Option B (Al$_2$O$_3$): Aluminium oxide reacts with hydrochloric acid (HCl) to form aluminium chloride and water, and it reacts with sodium hydroxide (NaOH) to form sodium aluminate and water. This confirms it is amphoteric.
3. Evaluate Option C (CuO): Copper(II) oxide is a metallic oxide that acts as a basic oxide; it reacts with acids but does not show acidic properties.
4. Evaluate Option D (K$_2$O): Potassium oxide is a strongly basic oxide (an alkali metal oxide). It reacts vigorously with water to form a strong base (KOH).

Conclusion

Based on the chemical properties, Al$_2$O$_3$ is the only oxide listed that demonstrates amphoteric behavior.

Exam Tip

Remember the mnemonic "Al-Zn-Pb" (Aluminium, Zinc, and Lead). If you see the oxides of these three metals in an exam question asking for an amphoteric substance, you can be confident that one of them is your answer!