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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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. For instance, carbonate has a great effect upon the diagram for uranium. The equation must be balanced for M, H, O and charge.

Using the expressions for the free energy in pourbaxi of potentials, the energy balance is given by a Nernst equation:.

The same values should be used for all species present in the system. In many cases, the possible conditions in a system are limited by the pourbaiix region of water.

The reaction equation is found to be:. The vertical axis is labeled E Diagramaa for the voltage potential with respect to the standard hydrogen electrode SHE as calculated by the Nernst equation.

As a function of temperature. On either side of the line, one form of the species will instead be said to be predominant. For the simple case of a thermodynamic system consisting of a metal M and water, various reaction equations may be written having the form:.

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. Wikimedia Commons has media related to Pourbaix diagrams.


There are three types of line boundaries in a Pourbaix diagram: 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. By using this site, you agree to the Terms of Use and Privacy Policy. From Wikipedia, the free encyclopedia. In these cases, pE is used instead of E H. As such a Pourbaix diagram can be read much like a standard phase diagram with a different set of axes.

Diagrama de Pourbaix

They thus give a guide to the stability of a particular metal in a specific environment. The reaction equation is written:. This will vary with temperature. Usually, the activity of diagrakas species is approximated as equal to the concentration for soluble species or partial pressure for gases.

The reaction equation may be written:. Archived copy as title Commons category link is on Wikidata. Predominant ion boundaries are represented by lines. In other projects Wikimedia Commons. Pourbaix diagrams are widely used to describe the chemical behaviour of chemical species in the hydrosphere.

Diagrama de Pourbaix – Wikipédia, a enciclopédia livre

Pourbaix diagrams are also known as E H -pH diagrams due to the labeling of the two axes. United States Government Printing Office.

Below this line, water will be reduced pourbaiix hydrogen, and it will usually not be possible to pass beyond this line as long as there is still water present to be reduced. Sometimes additional lines are drawn for other concentrations. Pourbaix diagrams have several uses, for example in corrosion studies, geoscience and in environmental studies. Retrieved from ” https: 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.


Environmental Chemistry – a global perspective 3rd ed. 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

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.

Archived from the original on Vertical, horizontal, and sloped. See diagrams at right. In order to draw the position of the lines with the Nernst equation, the activity of the chemical species at equilibrium must be defined. This page was last edited on 26 Decemberpourbaiz The diagrams are named after Marcel Pourbaix —the Russian -born, Belgian chemist who invented them. 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.

Diagrama de Pourbaix – Viquipèdia, l’enciclopèdia lliure

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. Views Read Edit View history. 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.