Class 11 Chemistry Redox Reactions Standard hydrogen electrode and its application

Standard hydrogen electrode and its application

Standard hydrogen electrode is the reference electrode that is used to calculate electrode potential of any electrode. It is also called as SHE or NHE.

Class_11_Chemistry_Redox_Reactions_SHE_1

                                               

This apparatus consists of beaker having 1 molar HCL solution. In it, a sealed tube having platinum wire is dipped. This platinum wire is further attached to platinum foil. This complete cell is connected to the cell. Then continuously hydrogen gas maintained at 1 atm is bubbled. Platinum foil here acts as a site of reaction.

The Standard electrode potential of SHE is zero volt. This SHE can act as anode or cathode, depending upon the half cell that is attached to it.

If it acts as cathode then following reaction occurs:

2H+  + 2e-  --> H2 (Reduction Occurs)

Hydrogen Ion    Hydrogen Gas

If it acts as anode then following reaction occur:

 2H        - 2e-  --> 2H+ (Oxidation occurs)

Hydrogen Gas       Hydrogen Ions

Applications:

  • This is used to calculate the electrode potentials of various half cells.

Let us calculate the electrode potential of Zn half-cell. The apparatus is set as shown:

 Class_11_Chemistry_Redox_Reactions_SHE

 

We known Zinc is more reactive than hydrogen, that is it has more tendency to loose electrons. Therefore, the following reactions occur:

Class_11_Chemistry_Redox_Reactions_Zinc_HalfCell

Likewise, if we calculate it for Copper half cell it comes out to be = 0.34 volt .This fact gave rise electrochemical series

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