Determination of Single Electrode Potential

chemistry-assignment:(Q.1)

It is not possible to measure directly the potential developed at interface of the metal gas and its ions in solution using voltmeter. Hence the electrode whose single electrode potential has to be determined is coupled with another electrode of known potential and the emf of the cell is determined by the potentiometeric method.

Normally SHE is used for coupling and in the electrochemical cell constructed, it acts either as a positive or negative electrode depending on the nature of the other electrode.

When SHE acts as positive electrode, then,

E.m.f = E^+ve - E^-ve

This means when the electrode potential is negative with respect to SHE, oxidation takes place at that electrode.

When SHE acts as negative electrode, then,

Emf = E^+ve - E^-ve

This means when the electrode potential is positive reduction takes place at the metal electrode.

Example:

electrode a cell made of a Zn electrode immersed in 1M ZnSO₄ is coupled with a S.H.E. The E.M.F. of the above cell is 0.76V. The direction of flow indicates that oxidation takes place so a standard reduction potential of -0.76V is given to it.