Van Arkel and Mond processes (purification of metals) (Mond: Ni + 4CO ⇌ Ni(CO)₄: volatile at 330 K, decomposes at 450 K. Van Arkel: Ti + 2I₂ →)
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Mond: Ni + 4CO ⇌ Ni(CO)₄ — volatile at 330 K, decomposes at 450 K. Van Arkel: Ti + 2I₂ → TiI₄ → Ti (hot filament)
What each symbol means
| Symbol | What it stands for |
|---|---|
| 330 K | Formation temperature for Ni(CO)₄ |
| 450 K | Decomposition temperature for Ni(CO)₄ |
| TiI₄ | Titanium tetraiodide — volatile intermediate in Van Arkel |
| Ni(CO)₄ | Nickel tetracarbonyl — volatile, toxic |
When to use this
Mond: ONLY for Ni (unique ability to form volatile carbonyl at low T). Van Arkel: for Ti, Zr, Hf — forms volatile iodide at moderate T, decomposes on hot tungsten filament.