ÎG = ÎG° + RT ln QrÎG: J/mol reaction; R: J·molâ»Âč·Kâ»Âč ; T: K; Qr: reaction quotient.
Use when: Compare written and standardized reactions consistently.
Ellingham, Pourbaix and Chaudron diagrams
Link diagram, environmental conditions and phase stability.
What is happening?
An Ellingham diagram represents the standard free energy of oxidation as a function of temperature. A Pourbaix diagram locates domains of stability in potentialâpH; a Chaudron diagram describes in particular equilibria of iron oxides with a reducing gas.
These maps indicate equilibrium trends under assumptions of pressure and activity. They do not alone predict the corrosion rate, the reduction time or the actual protection of a layer.
The formulas, with their conditions.
E = E° â (RT/nF) ln QrE: V; n: number dâelectrons; F: C/mol.
Use when: Nernst equation for a half-reaction written in the reduction direction.
Where is this principle used?
Reduction and smelting plant
Choose a reducing potential and compare affinities for oxygen.
Hydrometallurgy and corrosion study
Identify possible areas of dissolution or passivation.
What to observe in the experiment
On each type of card, name the two axes before looking for a stable phase. Then distinguish stability and speed of evolution.
References and readings
This sheet explains the principles and their assumptions. Educational simulation can simplify the process; an industrial model requires suitable data and validation.
Have you understood the essentials?
Only one correct answer per question. Answer all three questions, then view the answer key.
Intu Lab · Understanding sheet · Kimba Christian