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In electrochemistry, the Nernst equation is a chemical thermodynamical relationship that permits the calculation of the reduction potential of a reaction (half-cell or full cell reaction) from the standard electrode potential, absolute temperature, the number of electrons involved in the redox reaction, and activities (often approximated by concentrations) of the chemical species undergoing ...
In aqueous solutions, redox potential is a measure of the tendency of the solution to either gain or lose electrons in a reaction. A solution with a higher (more positive) reduction potential than some other molecule will have a tendency to gain electrons from this molecule (i.e. to be reduced by oxidizing this other molecule) and a solution with a lower (more negative) reduction potential ...
Especially in proteins, electron transfer often involves hopping of an electron from one redox-active center to another one. The hopping pathway, which can be viewed as a vector, guides and facilitates ET within an insulating matrix. Typical redox centers are iron-sulfur clusters, e.g. the 4Fe-4S ferredoxins. These sites are often separated by ...
When an oxidizer (Ox) accepts a number z of electrons ( e −) to be converted in its reduced form (Red), the half-reaction is expressed as: Ox + z e − → Red. The reaction quotient (Q r) is the ratio of the chemical activity (a i) of the reduced form (the reductant, a Red) to the activity of the oxidized form (the oxidant, a ox).
n = number of electrons transferred in the redox event (usually 1) A = electrode area in cm 2; F = Faraday constant in C mol −1; D = diffusion coefficient in cm 2 /s; C = concentration in mol/cm 3; ν = scan rate in V/s; R = Gas constant in J K −1 mol −1; T = temperature in K; The constant with a value of 2.69×10 5 has units of C mol − ...
An E h of zero represents the redox couple of the standard hydrogen electrode H + /H 2, [8] a positive E h indicates an oxidizing environment (electrons will be accepted), and a negative E h indicates a reducing environment (electrons will be donated). [1] In a redox gradient, the most energetically favorable chemical reaction occurs at the ...
Such reactions can also be quite complex, involving many steps. The mechanisms of electron-transfer reactions occur by two distinct pathways, inner sphere electron transfer [21] and outer sphere electron transfer. [22] Analysis of bond energies and ionization energies in water allows calculation of the thermodynamic aspects of redox reactions. [23]
In outer sphere redox reactions no bonds are formed or broken; only an electron transfer (ET) takes place. A quite simple example is the Fe 2+ /Fe 3+ redox reaction, the self exchange reaction which is known to be always occurring in an aqueous solution containing the aquo complexes [Fe(H 2 O) 6] 2+ and [Fe(H 2 O)6] 3+.