Ellingham Diagram — Predicted 2026
AI-Predicted Question Angles for UPSC 2026
Identifying reducing agent for specific metal oxides at different temperatures.
highThis is a core application of the Ellingham diagram. Questions will likely present a scenario with a metal oxide and ask which reducing agent (C, CO, or another metal) would be effective at a given temperature, requiring students to interpret crossing points and relative line positions. For instance, 'Which reducing agent is suitable for $ZnO$ at $1200^circ C$?' or 'Why is CO preferred over C for $Fe_2O_3$ reduction below $800^circ C$?'
Conceptual questions on the significance of slope and phase transitions.
mediumUnderstanding why lines slope upwards or downwards (related to $\Delta S$) and how phase changes (melting/boiling) affect the slope are fundamental. A question might ask about the change in slope when a metal melts or about the entropy change for a specific oxidation reaction based on its line's slope. This tests a deeper thermodynamic understanding beyond just reading the diagram.
Numerical problems involving calculation of overall $\Delta G^circ$ for a reduction reaction.
mediumWhile less frequent than conceptual questions, numerical problems testing the calculation of $\Delta G^circ$ for a coupled reaction are possible. Students would be given $\Delta G^circ$ values for two oxide formations at a specific temperature and asked to calculate the $\Delta G^circ$ for the reduction of one oxide by the metal of the other, or by carbon/CO. This tests the ability to apply the principle of subtracting $\Delta G^circ$ values correctly.
Questions on the limitations of the Ellingham diagram.
highThe distinction between thermodynamic feasibility and kinetic feasibility is a common point of confusion and a frequent trap in NEET. Questions often probe whether the diagram provides information about reaction rates or activation energy. Emphasizing that it's purely a thermodynamic tool is key.