An oxide has the following properties. It I. is a white powder II. reacts with HCI. III. reacts with NaOH IV. is insoluble in water The oxide is

Analyze the question: We're given four properties of an oxide and asked to classify it. The key clues are properties II and III: it reacts with both an acid (HCl) and a base (NaOH).

Concept: Types of oxides

| Type | Behavior | Examples | |---|---|---| | Basic/alkaline | Reacts with acids only (alkaline if it dissolves in water) | Na₂O, CaO, MgO | | Acidic | Reacts with bases only | CO₂, SO₂, P₄O₁₀ | | Neutral | Reacts with neither | CO, H₂O, N₂O | | Amphoteric | Reacts with both acids and bases | ZnO, Al₂O₃, PbO |

Step-by-step solution

1. White powder: this is true of ZnO and Al₂O₃, so it doesn't rule anything out.
2. Reacts with HCl: this shows basic character, which rules out acidic and neutral oxides. • ZnO + 2HCl → ZnCl₂ + H₂O
3. Reacts with NaOH: this shows acidic character, which rules out purely basic/alkaline oxides. • ZnO + 2NaOH + H₂O → Na₂[Zn(OH)₄]
4. Insoluble in water: this rules out an alkaline oxide, since alkaline oxides dissolve in water to form hydroxides (e.g. Na₂O + H₂O → 2NaOH).

Reacting with both an acid and a base is the definition of an amphoteric oxide. An example is zinc oxide or aluminium oxide.

Answer: B (amphoteric)

Exam tip: Remember "amphoteric = both." When a question says an oxide reacts with both an acid and an alkali, think of ZnO, Al₂O₃, PbO (a mnemonic: "Zebras, Ants and Pigs are amphoteric"). Also, if it reacts with both, you can ignore details like color and solubility.