2018 O Level Chem P1 Q29 — Metals / Reactivity Series Solution
Question
Pieces of lead, magnesium, iron and an unknown metal, X, were placed separately in test-tubes containing aqueous solutions of their ions. The following observations were made. What is the correct order of reactivity of the metals?
Correct answer: A
Video Solution
Explanation
Answer: A (Mg > Fe > X > Pb). A metal reacts with the solution of another metal's ions only if it is more reactive than that metal.
From the results: Mg reacts with \(\text{Pb}^{2+}\), \(\text{Fe}^{2+}\) and \(\text{X}^{2+}\), so Mg is the most reactive. Fe reacts with \(\text{Pb}^{2+}\) and \(\text{X}^{2+}\) (but not \(\text{Mg}^{2+}\)), so Fe is above both Pb and X. X reacts only with \(\text{Pb}^{2+}\), so X is above Pb but below Fe. Pb reacts with none, so it is the least reactive.
The order is Mg > Fe > X > Pb. Answer A.
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