Science (086) — AI-generated practice question

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

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

At the ionic level, iron atoms lose electrons and enter the solution as Fe²⁺ ions, forming iron sulphate (FeSO₄). Simultaneously, Cu²⁺ ions from the solution gain electrons and get deposited as copper metal on the nail. This deposited copper gives the nail a brownish coating. As Cu²⁺ ions are consumed and replaced by Fe²⁺ ions, the concentration of copper sulphate decreases, causing the blue colour to fade.

Source: Chapter 1, Section 1.2.3 — Displacement Reaction

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• The examiner expects you to name this as a displacement reaction and write the equation (1 mark).
• You must explain both observations separately: the brownish coating (Cu deposited) and the fading blue colour (Cu²⁺ ions replaced by Fe²⁺) — likely 1 mark each.
• Mentioning electron transfer (Fe loses electrons → Fe²⁺; Cu²⁺ gains electrons → Cu) earns the "atomic/ionic level" mark.
• Do not confuse this with rusting; this is a chemical displacement, not corrosion.