Science
(a) "Displacement reactions also play a key role in extracting metals in the middle of the reactivity series." Justify this statement with two examples.
(b) Why can metals high up in the reactivity series not be obtained by reduction of their oxides by carbon ?
Answer
(a) Metals in the middle of the reactivity series are usually obtained from their compounds using displacement reactions, where a more reactive element displaces a less reactive metal from its compound. For example:
Iron is obtained from its oxide using carbon monoxide as the reducing agent:
Fe2O3 + 3CO → 2Fe + 3CO2Zinc oxide is reduced by carbon to form zinc metal:
ZnO + C → Zn + CO
(b) Metals high up in the reactivity series such as sodium, potassium, calcium, magnesium and aluminium cannot be obtained by reducing their oxides with carbon because they have a strong affinity for oxygen. Their oxides are very stable and carbon is not reactive enough to displace these metals. Therefore, such metals are extracted by electrolysis of their molten compounds.
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