Science (086) — AI-generated practice question

(a) Oxidation is the gain of oxygen or loss of hydrogen by a substance.
Reduction is the loss of oxygen or gain of hydrogen by a substance.
Example of oxidation: $2\text{Cu} + \text{O}_2 \xrightarrow{\Delta} 2\text{CuO}$ (copper gains oxygen)
Example of reduction: $\text{CuO} + \text{H}_2 \xrightarrow{\Delta} \text{Cu} + \text{H}_2\text{O}$ (CuO loses oxygen)

(b) The balanced chemical equation for recovery of silver is:

$$2\text{AgNO}_3(aq) + \text{Cu}(s) \rightarrow \text{Cu(NO}_3)_2(aq) + 2\text{Ag}(s)$$

Type of reaction: Displacement reaction (copper displaces silver from silver nitrate solution).

(c) Metal X is copper (Cu). The black oxide formed is copper(II) oxide (CuO).

Reaction 1 (heating in air):
$$2\text{Cu} + \text{O}_2 \xrightarrow{\Delta} 2\text{CuO}$$

Reaction 2 (hydrogen passed over CuO):
$$\text{CuO} + \text{H}_2 \xrightarrow{\Delta} \text{Cu} + \text{H}_2\text{O}$$

In Reaction 2: H₂ is oxidised (gains oxygen); CuO is reduced (loses oxygen). This is a redox reaction.

Source: Chapter 1, Section 1.2.5 Oxidation and Reduction

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• (a) Always give both definitions together and use examples directly from the textbook (Activity 1.11). Examiners want the gain/loss language precisely.
• (b) This equation is directly from Exercise Q.14. Remember copper forms Cu(NO₃)₂ and silver is displaced as solid. Naming the reaction type is compulsory.
• (c) The identity of 'X' as copper comes from Activity 1.11. You must write both equations and explicitly state which substance is oxidised and which is reduced in Reaction 2 — that is the scoring point examiners specifically check.