Ch 6 covers metallurgy — the general principles and processes for extracting metals from their ores: concentration, extraction (using thermodynamic and electrochemical principles), and refining.
Concentration: gravity separation, magnetic, froth flotation (sulphide ores), leaching (Al from bauxite using NaOH). Calcination (heating without air), roasting (heating with air). Reduction: carbon (Fe from Fe₂O₃), CO, Al (thermite), electrolysis (Al from Al₂O₃). Ellingham diagram: lower ΔG° line reduces the upper.
Distillation (Zn), liquation (Sn), electrolytic refining (Cu — impure anode, pure cathode, CuSO₄ electrolyte). Zone refining (Ge, Si): impurities concentrate in molten zone. Vapour-phase refining: Mond process (Ni + CO → Ni(CO)₄), van Arkel (Ti + I₂ → TiI₄).
Download: https://ncert.nic.in/textbook/pdf/lech106.pdf | Part I: https://ncert.nic.in/textbook/pdf/lech1ps.zip
The Ellingham diagram plots ΔG° (Gibbs free energy of oxide formation) vs temperature for different metals. A metal whose oxide line is lower can reduce the oxide of a metal whose line is higher. Example: Al line is below Cr₂O₃ line, so Al reduces Cr₂O₃ (thermite process). The diagram helps predict feasibility of reduction.
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