In the reaction: CuO(s) + H₂(g) → Cu(s) + H₂O(l), which substance is reduced? (A) H₂ (B) H₂O (C) Cu (D) CuO

Question

In the reaction: CuO(s) + H₂(g) → Cu(s) + H₂O(l), which substance is reduced?
(A) H₂
(B) H₂O
(C) Cu
(D) CuO

Accepted Answer

## Model Answer **(D) CuO** In the reaction, CuO loses oxygen to form Cu, so CuO is **reduced**. (Reduction = loss of oxygen.) Source: Chapter 1, Section 1.2.5 Oxidation and Reduction --- ## Explanation Examiners expect you to recall the definition: **reduction = loss of oxygen**. In this reaction, CuO → Cu (oxygen is removed), so CuO is reduced. H₂ gains oxygen to form H₂O, so H₂ is oxidised. This is a classic redox (oxidation-reduction) reaction example directly from the textbook (equation 1.29/1.30).

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