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The link between cell potential & standard potential, as well as the activity of electro-active species, is defined by the Nernst equation. It connects the standard cell potential to the effective concentrations of the parts of a cell reaction. In this article, we will discuss Nernst equation applications which include aquatic environment and oxygen, applications of analytical chemistry, titrations through potentiometry, PH measurement, ion-selective electrodes and nerve conduction.
Nernst Equation Definition
The Nernst equation is a chemical thermodynamic connection in electrochemistry that allows the computation of a reaction’s reduction potential from the basic electrode potential, the number of electrons engaged in the oxidation-reduction, absolute temperature, and actions of the chemical species enduring oxidation and reduction.
Walther Nernst, (German physical chemist) devised the equation, which was then named after him.
Nernst Equation Applications
The Aquatic Environment And Oxygen, Nernst Equation Application
The availability of atmospheric oxygen has a significant impact on the redox characteristics of the aquatic environment. Natural waters are exposed to the atmosphere directly / indirectly, and, by implication, aerobic species.
This is because it is a very strong oxidising agent and consequently a low-lying sink for electrons from almost all elements and organic molecules. Protected areas of the environment are equally essential because it is only here that these electrons are accessible in sufficient quantities to provide the “reducing” conditions required for activities ranging from photosynthesis to nitrogen-fixing.
Applications Of Analytical Chemistry
A substantial part of chemistry is involved with estimating the concentration of ions in the solution, either directly or indirectly. Any approach that can provide such evaluations with very basic physical procedures will almost certainly be extensively used. Although the Nernst equation links cell potentials to ionic activity rather than concentration, the discrepancy between them is minimal in solutions with total ionic concentration levels of less than around 10–3 M.
Titrations Through Potentiometry
Because of the existence of other ions and a lack of knowledge regarding activity coefficients, precise estimation of an ion concentration by accurate detection of a cell potential is unachievable in many instances. In such circumstances, titration with another ion can frequently be used to indirectly determine the ion. Titration with a strong oxidising agent like Ce4+, for instance, can reveal the original concentration of an ion like Fe2+.
PH Measurement As Nernst Equation Application
A hydrogen electrode provides a direct measurement of H+ and consequently of –log H+, which would be the pH, because pH is defined based on hydrogen ion activity rather than concentration. All that is required is the measurement of a cell’s voltage.
The Glass Electrode Used For PH Measurement
It was discovered in 1914 that a thin glass coating encompassing a solution of HCl could generate a potential that differs from the h+ ions activity, in a similar way to the hydrogen electrode. Glass electrodes are mass-produced in large quantities for use in both laboratories and the field. They have an Ag-AgCl reference electrode built in that is in touch with the HCl solution contained within the membrane.
A glass electrode’s potential is determined by a variant of the Nernst equation that is very identical to that of a conventional hydrogen electrode, only without the H2:
Emembrane = A + (RT/F) ln ( {H+} + B )
where A & B are constants that vary depending on the glass membrane.
Electrodes That Are Ion-Selective
The glass electrode’s membrane allows hydrogen ions to move through it and adjust the electrode’s potential whilst blocking other cations from doing the same. As a result, a glass electrode becomes a type of ion-selective electrode.
Since around 1970, many additional membranes with identical selectivities to several other ions have been produced. These are used in a variety of industrial, environmental and biochemical applications.
Nerve Conduction As A Nernst Equation Application
Signals are sent via the nervous system not by charge carriers moving through the nerve, but rather by waves of various ion concentrations travelling down the length of the nerve. Protein-based channels & ATP-activated ion pumps specific to the K+ and Ca2+ ions minimise concentration gradients.
Our nerves are commonly thought of as the body’s wiring, however, the “electricity” they send is a quickly travelling wave of depolarization including the movement of ions across the neuron membrane, not a stream of electrons.
The typical potential difference between both the inner and outer sections of nerve cells is around –70 mv. A lowering of this potential difference to around –20 mv initiates nerve impulse transmission. The inflow of these ions induces the membrane potential of the neighbouring segment of the nerve to collapse, resulting in an effect that is transferred along the nerve’s length.
Conclusion
Here’s a quick summary of Nernst equation applications.
Although atmospheric oxygen is a powerful oxidizer, in the absence of a proper catalyst, the redox reaction is usually too slow to notice. Solubility products are frequently determined by building a cell with the sparingly soluble salt as one of the electrodes as well as the net cell equation corresponding to the solubility reaction. Potentiometric titrations are commonly employed to determine the amounts of easily oxidised or reduced species. The pH is measured using an electrode consisting of a layer of glass membrane wherein Na+ ions are swapped for H+. Nerve conduction is governed by the coordinated activity of active channels that regulate the movement of ions (mostly K+ and Na+) across the membrane covering the nerve, rather than by a current that flows through the nerve.
