Science (086) — AI-generated practice question

When copper(II) oxide (CuO) is heated with hydrogen gas, copper(II) oxide is reduced.

The reaction is:

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

Reason: Copper(II) oxide loses oxygen during this reaction (it goes from CuO to Cu). Since reduction is defined as the loss of oxygen, copper(II) oxide undergoes reduction. (Hydrogen gains oxygen and is oxidised.)

Source: Chapter 1, Section 1.2.5 — Oxidation and Reduction

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• The examiner wants you to name the substance (CuO) and give the reason in terms of gain/loss of oxygen — both are needed for full marks.
• Write the equation as supporting evidence; it makes the answer clear and earns the equation mark.
• The key definition to quote: "If a substance loses oxygen during a reaction, it is said to be reduced."
• Avoid saying "copper is reduced" — be precise: copper(II) oxide is reduced. Copper is the product after reduction.