Science — CBSE Class 10 board question

(a) Metals in the middle of the reactivity series (e.g., iron, copper) can be extracted using displacement reactions where a more reactive metal displaces them from their salt solutions.

Example 1: $\text{Fe}_2\text{O}_3 + 2\text{Al} \rightarrow \text{Al}_2\text{O}_3 + 2\text{Fe}$
(Aluminium displaces iron from iron oxide — thermite reaction)

Example 2: $\text{CuSO}_4(aq) + \text{Fe}(s) \rightarrow \text{FeSO}_4(aq) + \text{Cu}(s)$
(Iron displaces copper from copper sulphate solution)

(b) Metals high up in the reactivity series (e.g., Na, K, Ca, Al) are very reactive and have a stronger affinity for oxygen than carbon does. Carbon cannot reduce their oxides because it is less reactive than these metals, so carbon reduction fails.

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• For (a), the examiner expects the term "displacement reaction" used correctly, with two balanced equations clearly showing a more reactive element displacing a less reactive one.
• For (b), the key idea is relative reactivity: carbon must be more reactive than the metal to reduce its oxide. Since Na, K, Ca, Mg, Al are more reactive than carbon, carbon cannot displace them. One clear reason + one example metal is enough for 1 mark.