Q1. [2] medium exam-ready
Zinc oxide reacts with both dilute hydrochloric acid and with sodium hydroxide solution. Write the balanced chemical equations for both reactions. What does this dual behaviour indicate about the chemical nature of zinc oxide?
Generated by claude-sonnet-4-6 · 2026-06-26 01:05 · grounding rag
Model Answer
With dilute HCl:
$$\text{ZnO} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2\text{O}$$
With sodium hydroxide:
$$\text{ZnO} + 2\text{NaOH} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\text{O}$$
Since zinc oxide reacts with both acids and bases, it is amphoteric in nature.
Explanation
- The examiner expects both balanced equations (1 mark) and the term amphoteric with a one-line explanation (1 mark).
- "Amphoteric" is the key word — do not write just "neutral" or "dual nature" without naming it.
- The sodium zincate formula (Na₂ZnO₂) must be correct; some boards also accept ZnO + 2NaOH → Na₂[Zn(OH)₄] — either is acceptable as long as it is balanced.
- These reactions are a classic example from the Acids, Bases and Salts chapter (Class 10 Chemistry).