Science (086) — AI-generated practice question

Reaction 1 – Zinc with dilute sulphuric acid:

$$\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2\uparrow$$

The other product formed is zinc sulphate (ZnSO₄), a salt.

Reaction 2 – Zinc with sodium hydroxide solution:

$$\text{Zn} + 2\text{NaOH} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2\uparrow$$

The other product formed is sodium zincate (Na₂ZnO₂).

What this reveals about zinc oxide:

In Reaction 1, zinc behaves like a typical metal (reacting with acid to give a salt and hydrogen). In Reaction 2, zinc also reacts with a base (NaOH) to produce hydrogen, which means it shows acidic character as well.

This tells us that zinc oxide (ZnO) is an amphoteric oxide — it reacts with both acids and bases to form salt and water. Zinc oxide is therefore an exception to the general rule that metallic oxides are basic. Most metal oxides are basic, but some (like ZnO and Al₂O₃) show both acidic and basic properties and are known as amphoteric oxides.

Source: Metals and Non-metals, Section 3.2.1 and 3.2.3; Chemical Equations, Section 1.1.2

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• The examiner expects both balanced equations written correctly — these fetch 1 mark each.
• Naming the other product in each reaction is explicitly asked — 1 mark each.
• The final point on amphoteric oxides ties everything together for the 5th mark. Use the word "amphoteric" — it is the textbook term.
• The equation for zinc + NaOH is less commonly drilled than zinc + acid, so practise writing sodium zincate (Na₂ZnO₂) correctly.
• Do not confuse the question: it asks what zinc's dual behaviour reveals about metallic oxides in general — the answer is that not all metallic oxides are purely basic; some are amphoteric.