General Principles and Processes of Isolation of Elements – Class 12 Chemistry Notes | Complete NCERT Summary

 πŸ§ͺ Chapter 6: General Principles and Processes of Isolation of Elements



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πŸ”Ή Introduction


This chapter deals with metallurgy – the process of extracting pure metal from its ores.


Metallurgy steps: Concentration → Extraction → Refining




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πŸ”Ή Occurrence of Metals


Native State: e.g., gold, platinum


Combined State: Most metals found as oxides, sulphides, carbonates, halides etc.




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πŸ”Ή Steps in Metallurgy


1️⃣ Concentration of Ore


Removes impurities (gangue).


Methods:


Gravity separation (hydraulic washing)


Magnetic separation


Froth flotation (for sulphide ores)


Leaching (for Al, Ag)




πŸ“Œ Diagram: Froth flotation process setup



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2️⃣ Extraction of Crude Metal


By reduction of oxides:


Using carbon (smelting)


Using more reactive metals (Al in thermite process)


By electrolytic reduction




πŸ“Œ Diagram: Blast furnace for iron extraction



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3️⃣ Refining of Metal


Distillation


Liquation


Electrolytic refining


Zone refining (for semiconductors like Si, Ge)



πŸ“Œ Diagram: Electrolytic refining of copper



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πŸ”Ή Thermodynamic Principles of Metallurgy


Based on Ellingham diagrams – plots Ξ”G vs T.


A metal can reduce another metal’s oxide only if its line lies below that of the other.



πŸ“Œ Diagram: Ellingham diagram (for exam concept)



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πŸ”Ή Extraction Examples:


A. Iron


Ore: Haematite (Fe₂O₃)


Furnace: Blast furnace


Main reactions: Reduction of Fe₂O₃ by CO



B. Aluminium


Ore: Bauxite (Al₂O₃·xH₂O)


Process: Bayer (for purification), Hall-HΓ©roult (for electrolysis)



C. Copper


Ore: Copper pyrite (CuFeS₂)


Steps: Roasting → Smelting → Bessemerisation → Electrorefining




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πŸ”Ή Uses of Aluminium Extraction – Hall-HΓ©roult Process


πŸ“Œ Diagram: Electrolytic cell for Al extraction



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πŸ”Ή Refining Techniques Summary Table


Method Principle Example


Distillation Boiling point difference Zn, Hg

Liquation Melting point difference Sn, Pb

Electrolytic Electrolysis Cu, Al

Zone refining Impurity moves with molten zone Si, Ge




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πŸ–Ό️ Important Diagrams to Include:


1. Froth flotation process



2. Blast furnace (iron)



3. Electrolytic refining of copper



4. Hall-HΓ©roult cell (Al extraction)



5. Ellingham diagram



6. Zone refining schematic




7. Table of ores and metals



8. Summary chart of metallurgy steps





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✍️ Written by: Shahid – Study with Shahid

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