Pattern 1: Ellingham Diagram (Most Frequent Sub-topic)
Question types:
- Why does C→CO line slope downward? ( > 0, extra mole of gas)
- Which metal can reduce which oxide? (lower line reduces higher line)
- Why is C effective at high temperature? (downward slope crosses metal oxide lines)
Key answer: "The C → CO line has negative slope because > 0 (1 mol solid + 1 mol gas → 2 mol gas), making more negative as T increases."
Pattern 2: Extraction Method Matching
Common question: "Which method extracts Al / Cu / Fe / Ni / Ti?"
| Metal | Extraction | Refining |
|---|---|---|
| Al | Hall-Heroult (electrolysis) | Hoopes |
| Cu | Roasting + self-reduction (Bessemer) | Electrolytic |
| Fe | Blast furnace (CO reduction) | BOF/puddling |
| Zn | Roasting + C reduction | Distillation |
| Ni | — | Mond process |
| Ti | — | Van Arkel |
Pattern 3: Concentration Method Identification
Question: "Which method concentrates sulphide / oxide / magnetic ores?" Answer: Sulphide → froth flotation; Oxide (dense) → hydraulic; Magnetic → magnetic separation
Pattern 4: Calcination vs Roasting Trap
The NEET trap: "Sulphide ores are converted to oxides by calcination/roasting?" Answer: Roasting (excess air, produces SO2). Calcination is for carbonate/hydrated ores only.
Pattern 5: Anode Mud
"The anode mud in electrolytic refining of copper contains ___?" Answer: Au and Ag (less electropositive, do not dissolve)