JEE Main · 2021 · 27 Jul 2021 · Shift 1 · General Principles and Processes of Isolation of Metals

The Ellingham diagram plots the standard free energy of formation of metal oxides against temperature. Because it is built entirely from $\Delta G^{\circ }$ values it shows whether a reduction is thermodynamically feasible and which metal lies low enough to reduce another metal's oxide, and the sharp breaks in slope mark the temperatures at which a reactant or product melts or boils, so the phase changes are read off directly. A free energy change fixes only the position of equilibrium, never the speed at which it is reached, which is governed by the activation energy. The statement that the Ellingham diagram provides an idea about the reaction rate is incorrect.