Download/Embed scientific diagram | Diagrama de Pourbaix del hierro  y voltaje en función del pH (línea azul). from publication: Síntesis de nanopartículas. Download scientific diagram | Diagrama de Pourbaix para especies de cloro considerando una [Cl-] TOT = mM a T = 25°C para la ferrita de manganeso . ESPECIE. ΔG° (cal/mol). Pb. 0. PbO. , Pb3O4. , Pb2O3. , PbO2. , Pb2+. -5, Pb4+. 72, H2O. , REACCIONES DE.
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In addition, changes in temperature and concentration of solvated ions in solution will shift the equilibrium lines in accordance with the Nernst equation. The reaction equation is:. As such a Pourbaix diagram can be read much like a standard phase diagram with a different set of axes. Views Poudbaix Edit View history.
From Wikipedia, the free encyclopedia. Pourbaix diagrams are widely used to describe the chemical behaviour of chemical species in the hydrosphere.
A simplified Pourbaix diagram indicates regions of “Immunity”, “Corrosion” and “Passivity”, instead of the stable species. Passivation occurs when the metal forms a stable coating of an oxide or other salt on its surface, the best example being the relative stability of aluminium because of the alumina layer formed on its surface when exposed to air.
This page was last edited on 26 Decemberat Pourbaix diagrams are also known as E H -pH diagrams due to the labeling of the two axes.
As a function of temperature. Immunity means that the metal is not attacked, while corrosion pouebaix that general attack will occur. The equation must be balanced for M, H, O and charge.
Below this line, water will be reduced to hydrogen, and it will usually not be possible to pass beyond this line as long as there is still water present to be reduced. The lines in the Pourbaix diagram show the equilibrium conditions, that is, where the activities are equal, for the species on each side of that line.
United Dizgramas Government Printing Office. Geological Survey water-Supply Paper Usually, the activity of a species is approximated as equal to diagrmas concentration for soluble species or partial pressure for gases. The vertical diagrxmas is labeled E H for the voltage potential with respect to the standard hydrogen electrode SHE as calculated by the Nernst equation.
Diagrama de Pourbaix – Wikipédia, a enciclopédia livre
Viagramas additional lines are drawn for other concentrations. Similarly to phase diagrams, they do not allow for reaction rate or kinetic effects. In these cases, pE is used instead of E H. In many cases, the possible conditions in a system are limited by the stability region of water. In order to draw the position of the lines with the Nernst equation, the activity of the chemical species at equilibrium must be defined.
The presence of trace amounts of certain species such as chloride ions can also greatly affect the stability of certain species by destroying passivating layers.
The reaction equation may be written:. In other projects Wikimedia Commons. Pourbaix diagrams have several uses, for example in corrosion studies, geoscience and in environmental studies. In the Pourbaix diagram for uranium, the dkagramas of stability of water are marked by the two dashed green lines, and the stability region for water falls between these lines.
A base-balanced equation can be converted fiagramas an acid-balanced equation using the equilibrium constant for the self-ionization of waterand only acid-balanced equations are considered below.
Above this line, water will be oxidized to form oxygen gas, and it will usually not be possible to diagrsmas beyond this line as long as there is still water present to be oxidized. The “H” stands for hydrogen, although other standards may be used, and they are for room temperature only. The diagrams are named after Marcel Pourbaix —the Russian -born, Belgian chemist who invented them.
Using the expressions for the free energy in terms of potentials, the energy balance is given by a Nernst equation:. Using the Nernst equation as above, but with an E 0 of 1. Environmental Chemistry – a global perspective 3rd ed. For the simple case of a diagrams system pourabix of a metal M and water, various reaction equations may be written having the form:.
They thus give a guide to the stability of a particular metal in a specific environment. Archived copy as title Commons category link is on Wikidata. This will vary with temperature. Wikimedia Commons has media related to Pourbaix diagrams. Archived from the original on