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E s is the reduction potential of A (if the electrolyte and the electrode are in their standard conditions, then this potential is a standard reduction potential). As E approaches E s, the current on the surface increases, and when E = E s, the concentration of A equals that of the oxidized/reduced A at the surface ([A] = [A −]). [4]
The exchange current is the current at equilibrium, i.e. the rate at which oxidized and reduced species transfer electrons with the electrode. In other words, the exchange current density is the rate of reaction at the reversible potential (when the overpotential is zero by definition).
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: + The reaction quotient (Q r), also often called the ion activity product (IAP), is the ratio between the chemical activities (a) of the reduced form (the reductant, a Red) and the oxidized form (the oxidant, a Ox).
The values below are standard apparent reduction potentials (E°') for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution. [1] [2] The actual physiological potential depends on the ratio of the reduced (Red) and oxidized (Ox) forms according to the Nernst equation and the thermal voltage.
Since Δ r G o = -nFE o, the electrode potential is a representation of the Gibbs energy change for the given reduction. The sum of the Gibbs energy changes for subsequent reductions (e.g. from O 2 to H 2 O 2, then from H 2 O 2 to H 2 O) is the same as the Gibbs energy change for the overall reduction (i.e. from O 2 to H 2 O), in accordance ...
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 ...
Absolute partial pressure 101.325 kPa (1.00000 atm; 1.01325 bar) for each gaseous reagent — the convention in most literature data but not the current standard state (100 kPa). Variations from these ideal conditions affect measured voltage via the Nernst equation .
This ongoing current in both directions is called the exchange current density. When the potential is set more negative than the formal potential, the cathodic current is greater than the anodic current. Written as a reduction, cathodic current is positive. The net current density is the difference between the cathodic and anodic current density.