Consider the reaction: CuO(s) + H₂(g) → Cu(s) + H₂O(l). Identify which substance is oxidised and which is red…

Question

Consider the reaction: CuO(s) + H₂(g) → Cu(s) + H₂O(l). Identify which substance is oxidised and which is reduced. Explain your reasoning using the definition of oxidation and reduction in terms of gain or loss of oxygen.

Accepted Answer

## Model Answer In the reaction CuO + H₂ → Cu + H₂O: - **H₂ is oxidised** — it gains oxygen to form H₂O. - **CuO is reduced** — it loses oxygen to form Cu. **Definition:** Oxidation is the gain of oxygen; reduction is the loss of oxygen. Since both occur simultaneously, this is a redox reaction. Source: Chapter 1, Section 1.2.5 Oxidation and Reduction --- ## Explanation Examiners award 1 mark each for correctly identifying the oxidised substance (H₂) and the reduced substance (CuO), with a brief reason linked to gain/loss of oxygen. Simply naming the substance without the reason may cost you the mark. Remember: in redox reactions, one reactant is always oxidised and the other is always reduced simultaneously.

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