80:(for example, "water molecules", "sodium ions", "electrons", etc.) has an electrochemical potential (a quantity with units of energy) at any given point in space, which represents how easy or difficult it is to add more of that species to that location. If possible, a species will move from areas with higher electrochemical potential to areas with lower electrochemical potential; in equilibrium, the electrochemical potential will be constant everywhere for each species (it may have a different value for different species). For example, if a glass of water has sodium ions (Na) dissolved uniformly in it, and an
417:(either of a corroding electrode, an electrode with a non-zero net reaction or current, or an electrode at equilibrium). In some contexts, the electrode potential of corroding metals is called "electrochemical corrosion potential", which is often abbreviated as ECP, and the word "corrosion" is sometimes omitted. This usage can lead to confusion. The two quantities have different meanings and different dimensions: the dimension of electrochemical potential is energy per mole while that of electrode potential is voltage (energy per charge).
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It is (in principle) easy to measure whether or not two regions (for example, two glasses of water) have the same electrochemical potential for a certain chemical species (for example, a solute molecule): Allow the species to freely move back and forth between the two regions (for example, connect
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that lets only that species through). If the chemical potential is the same in the two regions, the species will occasionally move back and forth between the two regions, but on average there is just as much movement in one direction as the other, and there is zero net migration (this is called
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of electrons (or any other species) is the total potential, including both the (internal, nonelectrical) chemical potential and the electric potential, and is by definition constant across a device in equilibrium, whereas the
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and a chemical potential can both give the same result: A redistribution of the chemical species. Therefore, it makes sense to combine them into a single "potential", the
125:"diffusive equilibrium"). If the chemical potentials of the two regions are different, more molecules will move to the lower chemical potential than the other direction.
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across membranes, in electroanalytical chemistry, and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of
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of the substance at the specified electric potential, where the substance is in a specified phase. Electrochemical potential can be expressed as
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per electron. In solid-state physics, the definitions are normally compatible with this, but occasionally the definitions are swapped.
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is applied across the water, then the sodium ions will tend to get pulled by the electric field towards one side. We say the ions have
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diffusive equilibrium, i.e., when there is a tendency for molecules to diffuse from one region to another, then there is a certain
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around the water, until there is equal concentration of sugar everywhere. We say that the sugar molecules have a "
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released by each net-diffusing molecule. This energy, which can sometimes be harnessed (a simple example is a
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Modeling water chemistry and electrochemical corrosion potential in boiling water reactors
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sugar on one side and none on the other side, each sugar molecule will randomly
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It is common in electrochemistry and solid-state physics to discuss both the
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Electrochemical potential is important in biological processes that involve
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of electrons is equal to the electrochemical potential minus the local
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605:– lecture notes from University of Illinois at Urbana-Champaign
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This article uses the electrochemistry definitions.
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579:Massachusetts Institute of Technology
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568:Grover, D. J. (1996).
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457:Reduction potential
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134:free energy
52:measure of
613:Categories
577:(Thesis).
468:References
148:See also:
409:The term
384:conserved
268:Φ
243:μ
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160:electrons
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