Electrolysis Definition

Definitions:

• Standard Electrode Potential:

It is the EMF of any given half cell which is measured by combining it with standard hydrogen electrode (an example of a reference electrode). It is represented by E°

• Standard Cell Potential:

It is the potential difference measured when two half cells, other than the standard hydrogen electrode, are combined together through an external circuit and a salt bridge. It is represented by E° cell.

• Salt Bridge: 

It is used to bring ions of two electrolytes of the two half cells in contact with each other. It is also involved in maintaining equilibrium between cations and anions in the two electrolytes. It is made by filling U-Shaped glass tube with filter paper which is then soaked in solution of KCL or KNO3. This is because these two are ions which will never participate in a reaction.

• Standard Hydrogen Electrode (S.H.E):

It is an example of a reference electrode which is used to measure standard electrode potentials of different half cells when they are combined with Standard Hydrogen Electrode. The cell is made by using a platinum electrode in a glass tube which is inverted over an electrolyte containing 1 mol/dm3 of aqueous Hydrogen ions with a supply of
 Hydrogen gas through an inlet at 298k and 1 atm pressure. S.H.E is conventionally considered as a left hand side electrode.

If any half cell with an E° value greater than  0.00  is combined with S.H.E then electrons travel from S.H.E to the positive half cell. While in case of half cells which are found with more negative E° value than S.H.E, the electrons travel to S.H.E resulting in a negative value of Standard Electrode Potential.