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SSC CGL
mediumQ. No. 14872

Which process is used to obtain chromium by reducing chromium(III) oxide with aluminium?

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Chromium can be obtained from chromium(III) oxide by the aluminothermic, or thermite, process. Finely divided aluminium reduces Cr₂O₃ in a highly exothermic reaction: Cr₂O₃ + 2Al → Al₂O₃ + 2Cr + heat. Aluminium has a stronger affinity for oxygen, so it removes oxygen from chromium oxide and releases molten chromium. The process is used for reducing oxides of metals whose extraction by carbon may be unsuitable. Froth flotation concentrates sulphide ores, zone refining purifies already-produced metals or semiconductors, and electrolysis is used for selected extraction or refining operations. The reaction and aluminium’s role are the main exam points. Concept depth: The aluminothermic process uses aluminium powder as a powerful reducing agent for certain metal oxides.

AElectrolysis
BFroth flotation
CAluminothermic (thermite) process
DZone refining
Correct Answer: Aluminothermic (thermite) processYour Answer: C

Explanation

Correct answer: Option C — Aluminothermic (thermite) process. Aluminium acts as the reducing agent and converts Cr₂O₃ to chromium while itself forming Al₂O₃. Redox and option analysis: Chromium changes from +3 in Cr₂O₃ to 0 in metallic chromium, so chromium is reduced. Aluminium changes from 0 to +3 in Al₂O₃, so aluminium is oxidised and acts as the reducing agent. Froth flotation concentrates sulphide ores; zone refining purifies an already produced material; electrolysis is a different extraction or refining route. Only the thermite option describes aluminium reduction of chromium oxide.

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FAQ

SSC CGL Chemistry FAQs

Common questions and clear answers for this topic.

Which process reduces chromium oxide with aluminium?

The aluminothermic, or thermite, process.

What is the thermite reaction for chromium?

Cr₂O₃ + 2Al → Al₂O₃ + 2Cr.

Which substance is the reducing agent in chromium thermite reduction?

Aluminium.

What is oxidised in the reaction?

Aluminium is oxidised from 0 to +3.

How many chemistry questions typically appear in the SSC CGL exam?

Chemistry usually contributes a handful of questions within the General Awareness section, generally covering basic concepts rather than calculation-heavy problems.

Which chemistry topics are most important for SSC CGL preparation?

Atomic structure, periodic table trends, acids-bases-salts, metals and non-metals, and carbon compounds are the areas that appear most consistently across past papers.

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