Science (086) — AI-generated practice question

The student's claim is incorrect.

Oxidation and reduction always occur simultaneously in a chemical reaction. If a substance gains oxygen (or loses hydrogen), it is oxidised; if a substance loses oxygen (or gains hydrogen), it is reduced. Such reactions are called redox reactions.

For example: $\text{CuO} + \text{H}_2 \xrightarrow{\text{Heat}} \text{Cu} + \text{H}_2\text{O}$

Here, CuO is reduced (loses oxygen) and H₂ is oxidised (gains oxygen) at the same time. One cannot occur without the other — the oxygen lost by one substance must be gained by another.

Source: Chapter 1, Section 1.2.5 — Oxidation and Reduction

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• The examiner expects students to clearly state the claim is wrong and explain why using the definition of oxidation and reduction from the textbook.
• The key concept: oxidation and reduction are complementary — oxygen lost by one reactant is gained by another. This is why such reactions are called redox reactions.
• Including the example reaction (CuO + H₂) with identification of which substance is oxidised and which is reduced scores full marks. Don't just define — apply the concept.