Take timed practice tests on Metallurgy and Qualitative Analysis for JEE Main and JEE Advanced with session-wise drills, score review, and explanation-led revision.
Six 20-question timed sessions plus a 60-question chapter module. Each item is original and reframed for copyright safety.
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1. The mineral from which a metal is extracted profitably is called:
Explanation: Ore: a mineral from which a metal can be extracted economically. Not all minerals are ores. Gangue: unwanted earthy impurities mixed with the ore. Flux: substance added to combine with gangue to form fusible slag (CaO for siliceous gangue: SiO₂ + CaO → CaSiO₃).
2. The froth flotation method is used to concentrate:
Explanation: Froth flotation: sulphide ore particles are wetted by oil (pine oil) and float with froth; gangue particles are wetted by water and sink. Used for CuFeS₂ (copper pyrites), PbS (galena), ZnS (zinc blende).
3. The thermite reaction is: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe. This demonstrates:
Explanation: Thermite reaction: Al displaces Fe from Fe₂O₃ because Al has a more negative ΔGf° for Al₂O₃ than Fe for Fe₂O₃ (Ellingham diagram). Very exothermic → molten Fe is produced. Used for welding railway tracks.
4. The Ellingham diagram plots ΔG° of oxide formation vs T. A metal can reduce another metal's oxide if:
Explanation: On the Ellingham diagram, if the ΔG° line of metal M is below the ΔG° line of metal oxide M'O, then M can reduce M'O. E.g., Al can reduce Fe₂O₃ (Al₂O₃ line is below Fe₂O₃ line at all temperatures).
5. H₂S in acidic medium precipitates which group of cations?
Explanation: Qualitative analysis groups: I — HCl precipitates Ag⁺, Pb²⁺, Hg₂²⁺. II — H₂S in dilute HCl (acidic) precipitates Cu²⁺, Pb²⁺, etc. (Ksp very small). III — (NH₄)₂S in NH₃ buffer precipitates Fe³⁺, Al³⁺, Cr³⁺ as hydroxides. IV — (NH₄)₂S in alkaline → ZnS, MnS, NiS, CoS. V — alkaline conditions → BaSO₄, CaCO₃. VI — Na, Mg remain.
6. In Zone refining (Van Arkel/Float zone), the principle used is:
Explanation: Zone refining: a heater moves slowly along the metal rod. Impurities have lower melting points → they concentrate in the melt and move to one end. Repeated passes give extremely pure metal. Used for Ge, Si (semiconductor grade), Ga, In.
7. The process of extracting crude metal from its oxide by heating with a reducing agent (like C or CO) is called:
Explanation: Smelting: ore oxide + reducing agent (C or CO) → metal + CO₂. Used for iron (Fe₂O₃ + 3CO → 2Fe + 3CO₂ in blast furnace), zinc (ZnO + C → Zn + CO). Roasting: heating sulphide ore in air → oxide + SO₂.
8. The Hall-Héroult process is used to extract:
Explanation: Hall-Héroult process: Al₂O₃ (alumina from bauxite by Bayer's process) is dissolved in molten cryolite (Na₃AlF₆) to lower the melting point. Electrolysis: cathode → Al³⁺ + 3e⁻ → Al (liquid). Anode → O²⁻ − 2e⁻ → O₂ (burns carbon anode). Cryolite lowers melting point from 2050°C to ~940°C.