Metallurgy Notes for Class 12, IIT JEE & NEET

The Ellingham diagram plots the standard Gibbs free energy change (ΔG°) of metal oxide formation against temperature. It helps predict which reducing agent can reduce a given metal oxide. If the ΔG° line of the reducing agent's oxide lies below that of the metal oxide at a given temperature, reduction is thermodynamically feasible. JEE Main tests this concept through interpretation questions almost every year

Cryolite (Na₃AlF₆) is added to lower the melting point of aluminium oxide from about 2050°C to approximately 950°C. This makes the electrolytic process commercially viable in terms of energy costs. The molten mixture also has better electrical conductivity than pure Al₂O₃ alone, which speeds up the electrolysis.

A mineral is any naturally occurring compound of a metal found in the Earth's crust. An ore is a mineral from which a metal can be extracted profitably and conveniently. All ores are minerals, but not all minerals are ores. For example, both clay and bauxite contain aluminium, but only bauxite is an ore because aluminium can be extracted from it economically.

Metallurgy is important for both. NEET typically asks 1 question from this chapter, usually focused on the extraction process of a specific metal (especially aluminium or copper) or the principle behind a refining method. NEET questions tend to be more direct and definition-based, while JEE questions test conceptual application and thermodynamic reasoning.

Based on NTA question paper patterns from 2019–2025, JEE Main typically includes 1–2 questions from Metallurgy per session. Topics with the highest frequency are Hall–Héroult process, froth flotation, zone refining, and Van Arkel method. Solving 5 years of previous papers for this chapter alone is sufficient coverage for most aspirants.

The Van Arkel method (vapour phase refining using volatile iodides) is used specifically for titanium (Ti) and zirconium (Zr). The crude metal reacts with iodine to form a volatile tetraiodide (e.g., TiI₄), which is then thermally decomposed on a hot tungsten filament, depositing pure metal. This method gives extremely high purity.