Electrode Potential


The electrode is the conductive rod that is in contact with a conductive electrolyte. It is a solid electric conductor that carries electric current into non-metallic substances. For example, when the copper rod is immersed in a solution of copper sulfate, it becomes an electrode.

Electrode Types

In an electrochemical cell, reduction and oxidation reactions take place at the electrodes. On this basis there are two types of electrodes:

1. Anode

The electrode at which oxidation is always or donation of electrons is called the anode.

2. Cathode

Unlike the anode, the electrode that always has a reduction or eclipse of electrons is called a cathode.

Electrode Potential

A potential difference develops between the electrode and the electrolyte which is called the electrode potential. When a metal rod is immersed in the ions of the same metal, the metal rod is charged relative to the billion, creating a difference between the metal and its ions solution. This generated potential is called electrode potential.
For example, if a rod of copper metal is immersed in a copper sulfate solution, the potential difference between copper and copper ions is called electrode potential. It is also called half-cell.electrode potential

Standard Electrode Potential

The standard electrode potential of an electric conductor rod is the difference produced between the conductor rod and the solution when an electric conductor (metal) rod is heated to 25 ° C in a solution of the same metal salt at a concentration of 1 molar.

Types of Electrode Potential

1. Oxidation Electrode Potential

When oxidation occurs at the electrode, the potential generated between the electrode and the villain is called the oxidation electrode potential.

2. Reduction Electrode Potential

When a reduction occurs at the electrode, the potential difference between the electrode and the solution is called the reduction electrode potential.

Standard or Reference Electrode

A standard half-cell is used to find the potential of any half-cell whose potential is fixed and known. This type of half cell is called a standard electrode. Hydrogen standard electrodes are used to measure the potential of an unknown half-cell with a coma whose potential is 0.

electrode potential
Silver-Sliver Chloride. AgCl + e-  Ag(s) +Cl- E0 = V. E (saturated KCl) = V. Calomel. Hg2Cl2 + 2e-  2Hg(l) +2Cl- E0 = V. E (saturated KCl) = V. saturated calomel electrode (S.C.E.)

Standard Hydrogen Electrode

The hydrogen electrode in which the pressure of the h2 gas is placed in an atmosphere and the concentration of hydrogen ion in the solution is 1 molar is called a standard hydrogen electrode. The electric carrying force of the electrode is assumed to be 0.00 bolts at each temperature. In the manufacture of standard hydrogen electrodes, platinum foil coated with platinum black is exposed to the valence of hydrogen ions with unit activation, and pure hydrogen gas flows at 1 atmospheric pressure. It is also called a normal hydrogen electrode.Standard hydrogen electrode potential

Electrode Potential Measurement

It is not possible to directly measure the potential of an independent electrode but the difference between the two electrodes can be measured correctly. This is called the indirect method of measurement of electrode potential. In this method, the metal electrode, whose potential is to be determined, is coupled to the electrode of known potential. An electrode with this known potential is called a reference or standard electrode. In this process, the metal electrode and the reference electrode are formed by forming a cell to determine the potential of the resulting cell. We already know the potential of the reference electrode, so with the help of the values ​​of these two, the potential of the metal electrode is calculated.

Measurement of Standard Electrode Potentials of Zinc

When a zinc metal standard electrode is connected to a hydrogen electrode, current flows from the hydrogen electrode to the electrode. When measured with a voltmeter, the difference of their potential is obtained as -0.76 Volt. The power always flows from an object with a higher potential to an object with a lower potential. Therefore, the standard electrode potential of which is less than the standard electrode potential of hydrogen.
Potential of the standard zinc electrode =

Potential of standard hydrogen electrode – the potential difference of the cell

Or                0.00 – 0.76 = -0.76 Volt.

Electrode Potential Sign Pattern

The standard electrode potential value is more positive for electrons, and the tendency for a reduction on the electrodes is higher. If the electrode potential value is less positive than this minus is positive then the tendency of oxidation is found to be higher on it.
The values ​​of oxidation potential and reduction potential are similar but their signs are opposite. For example, the oxidation potential of copper is -0.34 Volt and the reduction potential is +0.34 Volt.

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