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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 physics and chemistry, the Nernst effect (also termed the first Nernst–Ettingshausen effect, after Walther Nernst and Albert von Ettingshausen) is a thermoelectric (or thermomagnetic) phenomenon observed when a sample allowing electrical conduction is subjected to a magnetic field and a temperature gradient normal (perpendicular) to each ...
The above equation is a modern statement of the theorem. Nernst often used a form that avoided the concept of entropy. [1] Graph of energies at low temperatures. Another way of looking at the theorem is to start with the definition of the Gibbs free energy (G), G = H - TS, where H stands for enthalpy.
The Nernst statement concerns thermodynamic processes at a fixed, low temperature, for condensed systems, which are liquids and solids: The entropy change associated with any condensed system undergoing a reversible isothermal process approaches zero as the temperature at which it is performed approaches 0 K.
at constant temperature and pressure, the thermodynamic voltage (minimum voltage required to drive the reaction) is given by the Nernst equation: = = where is the Gibbs energy and F is the Faraday constant. The standard thermodynamic voltage (i.e. at standard temperature and pressure) is given by:
Variations from these ideal conditions affect measured voltage via the Nernst equation. Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆G°) must satisfy ∆G° = – z FE°,
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Nernst lamps did not use a glowing tungsten filament. Instead, they used a ceramic rod that was heated to incandescence.Because the rod (unlike tungsten wire) would not further oxidize when exposed to air, there was no need to enclose it within a vacuum or noble gas environment; the burners in Nernst lamps could operate exposed to the air and were only enclosed in glass to isolate the hot ...