ELECTROCAPILLARY PHENOMENON OF SURFACE

The surface excess of a particular species is the of that species present at the surface relative to the amount that would have been pressure had there been no electrical double layer surface.

                                 Surface excess is based on the surface tension, a property that depends on surface excess. The surface tension, arises from the anisotropic forces at a an interphase and the forces are affected by the particles into interphase and therefore surface tension can be related to the surface excess. The surface excess concept is useful in the understanding of the distribution of particles at an interface.

The double layer region in an electrode - electrolyte interface has free energy compare of the phase. This excess free energy per unit surface of the interface called surface tension or interfacial tension.

                                   Interfacial tension can be quantities like surface excess and potential difference. A quantities relation among surface tension, excess charge on metal, solution composition and surface excess can be using thermodynamics.

The measurement of the interfacial tension as a function of applied potential will give some idea about the distribution of particles at the interface.

                                 The surface tension at the metal - electrolyte phase boundary of the potential. The phenomenon was first studied by quantitatively by Lippmann is called electrocapillary.

Electrocapillary means the measurement of surface tension of Hg as a function of potential difference across the surface. The induced charge is equal and opposite to that on the electrolyte side of the phase boundary.

As a result of the induced change a, separation of charge has occurred across the electrode - electrolyte interface and a net charge of one side one and another sign of the electrolyte side. However the interphase region as a whole is electrically neutral.

When the charges are separated a potential different develops across the interface. The electric forces separate across the electrode - electrolyte instead constitute a electrical double layer across the interface. This situation of the interface constituent what is called an electrical double layer. It can also be called electrified interface. 

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