Science (086) — AI-generated practice question

Highly reactive metals like sodium and aluminium have a greater affinity for oxygen than carbon does. Therefore, carbon cannot reduce their oxides — it is not a strong enough reducing agent to displace these metals from their oxides.

The method used to extract such metals is electrolytic reduction (electrolysis). For example, sodium is extracted by electrolysis of molten sodium chloride. At the cathode, sodium is deposited:

$$\text{Na}^+ + e^- \rightarrow \text{Na}$$

At the anode, chlorine is liberated:

$$2\text{Cl}^- \rightarrow \text{Cl}_2 + 2e^-$$

Similarly, aluminium is obtained by electrolytic reduction of aluminium oxide.

Source: Chapter 3, Section 3.4.5 — Extracting Metals towards the Top of the Activity Series

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• Why carbon fails: The key reason is affinity for oxygen — Na and Al hold oxygen more strongly than carbon does, so carbon cannot "pull" oxygen away from their oxides. State this clearly for full marks.
• Method name: "Electrolytic reduction" or "electrolysis" — both are accepted. Naming the method earns 1 mark; the reason earns 1–2 marks.
• Equations: Including the cathode/anode half-reactions adds precision and is expected at this level; they demonstrate understanding of the process.
• Avoid vague answers like "carbon is not strong enough" without linking it to oxygen affinity.