What is electrode potential?

In all chemical sources of the electric power quite difficult phenomena of dissolution of metals in elektroliyota are used. The metal plate lowered in solution of the soyola in a varying degree aims to be dissolved in it. This aspiration sometimes is called elasticity the metal rastvoreyoniya.

Схема установки для измерения потенциалов

The scheme of installation for measurement of potentials: 1 - hydrogen electrode; 2 - siphon; 3 - the metallic electrode at which potential is measured; 4 - siphon.

For example, the zinc plate in solution of sulfate ZnS04 zinc otyodat in zinc particle solution in the form of positively charged ions therefore on the zinc plate  the surplus of free electrons is formed and it is loaded negatively, and in the liquid layer near the surface of zinc the surplus of poyolozhitelny ions is formed and, therefore, this layer is loaded positively. It puyoty on border of liquid and metal vozyonikat the double electric layer — the layer from spatially razdeyolenny charges of the opposite sign.

These charges will counteract further transition of metal to solution: the negative charge of the plate holds the positively ionized atom of metal, and the positive charge of the elektroliyot pushes away the metal ion back on the plate. In other words, electric field of the double layer on border metal — liquid counteracts further transition of ions of metal to the rayostvor.

Balance between the powers of aspiration of metal, chemical by the nature, to pass into solution and the elektyorichesky forces counteracting them is established.

Therefore, the metallic electrode has in relation to electrolyte certain electrode (differently electrochemical) the potential depending on material of the electrode and composition of electrolyte.

Electrode potentials have positive value when positively ionized atoms from solution pass to the electrode, loading it is positive, and the electrolyte layer — is negative, for example, when the copper plate is submerged in doyostatochno the concentrated solution of sulfate CuSO* copper.

To measure the electrode potential of any metal, не­обходимо to place the second electrode which will have the certain electrode potential depending on its material in electrolyte. Therefore, it is neposredyostvenno possible to measure only the algebraic sum of two electrode potentials. Electrode potenyotsiala of different materials are determined by this reason in relation to the standard (hydrogen) electrode which potential is usyolovno taken for zero. For example, the electrode potential of zinc measured thus in solution of the corresponding metal salt — 0,76 in, copper +0,34 in, silver of +0,8 century.

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