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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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. The equation must be balanced for M, H, O and charge.

Pourbaix diagram

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. The “H” stands for hydrogen, although other standards may be used, and pouurbaix are for room temperature only. Archived from the original on 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.

The reaction equation may be written:. The reaction equation is found to be:.

Diagrama de Pourbaix – Viquipèdia, l’enciclopèdia lliure

Using the Nernst equation as above, but with an E 0 of 1. From Wikipedia, the free encyclopedia.

Sometimes additional lines are drawn for other concentrations. As such a Pourbaix diagram can be read much like a df phase diagram with a different set of axes.

They thus give a guide to the stability of a particular metal in a specific environment. United States Government Printing Office.

Pourbaix diagram – Wikipedia

In many cases, the possible conditions in a system are limited by the stability region of water. Predominant ion boundaries are represented by lines. A simplified Pourbaix diagram indicates regions of “Immunity”, “Corrosion” and “Passivity”, instead of the stable species. Views Read Edit View history.


On either side of the line, one form of the species will instead be said ;ourbaix be predominant. By using this site, you agree to the Terms of Use and Privacy Policy. Environmental Chemistry – a global perspective 3rd ed.

Diagrama de Pourbaix

A base-balanced equation can be converted to an acid-balanced equation using the equilibrium constant for the self-ionization of waterand only acid-balanced equations are considered below.

The vertical axis is labeled E H for the voltage potential with respect to the standard hydrogen electrode SHE as calculated by the Nernst equation. As a function of temperature.

For the simple case of a thermodynamic system consisting of a metal M and water, various reaction equations may be written having the form:. Usually, the activity of a species is approximated as equal to the concentration for soluble species or partial pressure for gases. This will vary with temperature. In addition, changes in temperature and concentration of solvated ions in solution will shift the equilibrium riagramas in accordance with the Nernst equation.

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. Below this line, water will be reduced to hydrogen, and it will usually not be possible to pass beyond diagramss line as long as there is still water present to be reduced.

Immunity means that the metal is not attacked, while corrosion shows that general attack will occur. 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 diagrramas on 26 Decemberriagramas Pourbaix diagrams are widely used to describe the chemical behaviour of chemical species in the hydrosphere.


Pourbaix diagrams have several diagramae, for example in corrosion studies, geoscience and in environmental studies. Archived copy as title Commons category link is fe Wikidata. Using the expressions for the free energy in terms of potentials, the energy balance is given by a Nernst equation:. For instance, carbonate has a great effect upon the diagram for uranium.

In these cases, pE is used instead of E H. Pourbaix diagrams are also known as E H -pH diagrams due to diagdamas 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.

There are three types of line boundaries in a Pourbaix diagram: Geological Survey water-Supply Paper The diagrams are named after Marcel Pourbaix —the Russian -born, Belgian chemist who invented them.

In other projects Wikimedia Commons. Retrieved from ” https: The reaction equation is:.

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. The same values should be used for all species present in the system.