Standard Hydrogen Electrode (SHE)/ Primary reference electrode | Gas electrode

This video describes the construction of standard hydrogen electrode. The half cell reactions are explained. The standard electrode potential of various electrodes can be determined using standard hydrogen electrode. The advantages and limitations of standard hydrogen electrode are also discussed.
H2 gas (1 atm.) passed through inverted glass tube (glass jacket) immersed in 1M HCl solution.
Electrical conductivity:
Pt wire connected to a Pt foil covered with spongy Pt (Pt black)Temperature – 25 oC
Primary reference electrode - It is a primary reference electrode, as it can be used to determine the standard electrode potentials of various electrodes.
Standard electrode potential – 0 volts
(at 25 oC and 1 atm. H2 passed through solution of 1M HCl)
When it acts as anode:
H2 gas gets adsorbed on finely divided Pt . H2 gas from Pt gets oxidised to form H+ ions and release electrons.
These electrons get accumulated on Pt.
Electrode representation/Half cell representation
When it acts as cathode:
The electrons enter through the Pt wire and reduces the H+ ions to form H2 gas.
Advantages of standard hydrogen electrode
The standard electrode potential is ‘0’ . Hence, in the determination of single electrode potential of an unknown electrode using SHE as the reference electrode, it is equal to the emf of the cell.
It can be used for the entire range of pH.
Limitations/Drawbacks of standard hydrogen electrode
It is cumbersome and difficult to construct SHE.
It is difficult to obtain high pure H2 gas and to maintain 1M HCl for a long time.
Since it is made of glass, care is needed to handle.
Pt is highly expensive and it may get poisoned by the impurities present in H2 gas and HCl.
It is not suitable for redox reactions.

Видео Standard Hydrogen Electrode (SHE)/ Primary reference electrode | Gas electrode канала Revathi Purushothaman