Using the reaction ZnO + C → Zn + CO as an example, explain why oxidation and reduction are said to occur simultaneously. Identify the substance oxidised and the substance reduced, giving a reason for each.
Generated by claude-sonnet-4-6 · 2026-06-26 00:54 · grounding rag
Model Answer
In the reaction ZnO + C → Zn + CO, oxidation and reduction happen at the same time (simultaneously) because one substance loses oxygen while another gains it in the same reaction.
- Carbon (C) is oxidised — it gains oxygen (from ZnO) to form CO.
- Zinc oxide (ZnO) is reduced — it loses oxygen to form Zn.
Since one substance cannot gain oxygen unless another loses it, oxidation and reduction always occur together. Such reactions are called redox reactions.
Source: Chapter 1, Oxidation and Reduction (gain/loss of oxygen)
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Explanation
- Examiners expect you to clearly state the definition: oxidation = gain of oxygen; reduction = loss of oxygen.
- You must name the specific substance oxidised and reduced with a reason (what oxygen did) — this earns separate marks.
- The key phrase to include is "simultaneously" or "at the same time," showing you understand why it's called a redox reaction.
- Do not mix up ZnO and C — C is oxidised, ZnO (or Zn) is reduced.