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Difficulty: EasyGeneral Principles of Metallurgy and Metal Extraction

Metals positioned near the top of the electrochemical reactivity series, such as sodium and aluminium, are extracted from their purified ores primarily through which method?

  1. Electrolysis of their molten compoundsAnswer
  2. B
    Reduction of their oxides using carbon monoxide
  3. C
    Roasting their sulfide ores directly in excess air
  4. D
    Thermal decomposition of their trioxocarbonate(IV) salts

Answer

Electrolysis of their molten compounds
Metals positioned high in the electrochemical series (such as sodium, potassium, calcium, and aluminium) have a strong affinity for oxygen and chlorine. Chemical reducing agents like carbon or carbon monoxide are weaker reducing agents than these metals and cannot reduce their oxides. Consequently, these metals are extracted by electrolysis of their molten (fused) ores or salts.

Step-by-Step Solution

1
Assess metal reactivity based on position in the electrochemical series
Sodium and aluminium are highly electropositive and hold onto oxygen/halogens strongly.
Metals at the top of the reactivity series form compounds with very high thermal and chemical stability.
2
Select the appropriate reduction method
Standard chemical reducing agents (such as carbon or hydrogen) are ineffective.
Only powerful electrical energy supplied during electrolysis of fused compounds can force electron gain at the cathode to yield free metal.

Key Concept

Selection of metal extraction method based on reactivity series
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Topics

General Principles of Metallurgy and Metal Extraction

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