Download/Embed scientific diagram | Diagrama de Pourbaix del hierro [12] 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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From Wikipedia, the free encyclopedia. Geological Survey water-Supply Paper As a function of temperature. In addition, changes in temperature and concentration of solvated ions in solution will shift the equilibrium lines in accordance with the Nernst equation.

Pourbaix diagram – Wikipedia

While such diagrams can be drawn for any chemical system, it is important to note that the addition of a metal binding agent ligand will often modify the diagram. Using the expressions for the free energy in terms of potentials, the energy balance is given by a Nernst poudbaix. A base-balanced equation diagranas be converted to an acid-balanced equation using the equilibrium constant for the self-ionization of waterand only acid-balanced equations are considered below.

See diagrams at right.

In the Pourbaix diagram for uranium, the limits of stability of water are marked by the two dashed green lines, and the stability region for water falls between these lines. This page was last edited on 26 Decemberat The reaction equation is:. 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. In other projects Wikimedia Commons.

Above this line, water will be oxidized to form oxygen gas, and it will usually not be possible to pass beyond this line as long as there is still water present to be oxidized. Pourbaix diagrams have several uses, for example in corrosion studies, geoscience and in environmental studies.


The “H” stands for hydrogen, although other standards may be used, and they are for room temperature only. Pourbaix diagrams are widely used to describe the chemical behaviour of chemical species in the hydrosphere. Environmental Chemistry – a global perspective 3rd ed. They thus give a guide to the stability of a particular metal in a specific environment.

Pourbaix diagrams are also known as E H -pH diagrams due to the labeling of the two axes. 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.

For instance, carbonate has a great effect upon the diagram for uranium. Sometimes additional lines are drawn for other concentrations. The same values should be used for all species present in the system. Usually, the activity of a species is approximated as equal to the concentration for soluble species or partial pressure for gases. In these cases, pE is used instead of E H.

Immunity means that the metal is not attacked, while corrosion shows that general attack will occur. There are three types of line boundaries in a Pourbaix diagram: The diagrams also do not take kinetic effects into account, meaning that species shown as unstable might not react to any significant degree in practice.

A simplified Pourbaix diagram indicates regions of “Immunity”, “Corrosion” and “Passivity”, instead of the stable species. This will vary with temperature.

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. Vertical, horizontal, and sloped. 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.


Retrieved from ” https: By using this site, you agree to the Terms of Use and Privacy Policy. The reaction equation may be written:. Using the Nernst equation as above, but with an E 0 of 1. Views Read Edit View history. Archived copy as title Commons category link is on Wikidata. Wikimedia Commons has media related to Pourbaix diagrams. For the simple case of a thermodynamic system consisting of a metal M and water, various reaction equations may be written having the form:.

The reaction equation is found to be:. Archived from the original on Using the Pourbaix diagram correctly will help shed light not only on the nature of the species present in the solution or sample but may also help to understand the reaction mechanism. United States Government Printing Office. Similarly to phase diagrams, they do not allow for reaction rate or kinetic effects.

Predominant ion boundaries are represented by lines. In order to draw the position of the lines with the Nernst equation, the activity of the chemical species at equilibrium must be defined. On either side of the line, one form of the species will instead be said to be predominant.

Diagrama de Pourbaix

In many cases, the possible conditions in a system are limited by the stability region of water. The equation must be balanced for M, H, O and charge.

The reaction equation is written:.