Science (086) — AI-generated practice question

Type of Reaction: This is a displacement reaction.

Reason for colour change: Iron displaces copper from copper sulphate solution because iron is more reactive than copper. The reaction is:

$$\text{Fe}(s) + \text{CuSO}_4(aq) \rightarrow \text{FeSO}_4(aq) + \text{Cu}(s)$$

The iron nails turn brownish because a layer of copper metal is deposited on them. The blue colour of copper sulphate solution fades because copper sulphate is consumed and green iron sulphate (FeSO₄) is formed in its place.

Source: Chapter 1, Section 1.2.3 – Displacement Reaction

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• 1 mark for naming the reaction type (displacement reaction).
• 1 mark for the balanced chemical equation (examiners expect it here).
• 1 mark for correctly explaining both colour changes — the brownish deposit on the nail (copper) AND the fading blue colour (copper sulphate being replaced by FeSO₄).

Common mistake: Students explain only one colour change and lose a mark. Always address both — the nail and the solution.