Science (086) — AI-generated practice question

Type of Reaction: Displacement reaction.

Iron (Fe) is more reactive than copper (Cu), so it displaces copper from copper sulphate solution. The reaction is:

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

Why the blue colour fades: Copper sulphate (CuSO₄) gives the solution its blue colour. As iron displaces copper, CuSO₄ is consumed and replaced by iron sulphate (FeSO₄), which is pale green. Since the concentration of CuSO₄ decreases, the blue colour of the solution gradually fades. Copper metal is deposited on the iron nail, turning it brownish.

Source: Chapter 1, Section 1.2.3 – Displacement Reaction

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• 1 mark for naming the reaction (displacement reaction).
• 1 mark for the balanced chemical equation.
• 1 mark for explaining the fading of blue colour — examiners want you to link it to the consumption of CuSO₄ and formation of FeSO₄. Just saying "copper is displaced" is insufficient; you must explain what happens to the blue-coloured ion.
• Always write the equation with state symbols — it signals precision to the examiner.