Galvani Potential - Relation To Measured Cell Potential

Relation To Measured Cell Potential

The Galvani potential difference is not measurable. The measured potential difference between two metal electrodes assembled into a cell does not equal the difference of the Galvani potentials of the two metals (or their combination with the solution Galvani potential) because the cell needs to contains another metal-metal interface, as in the following schematic of a galvanic cell:

M(1) | S | M(2) | M(1)'

where:

  • M(1) and M(2) are the two different metals,
  • S denotes the electrolyte,
  • M(1)' is the additional metal (here assumed to be the metal (1)) that must be inserted into the circuit to close it,
  • the vertical bar, |, denotes a phase boundary.

Instead, the measured cell potential can be written as:

E^{(2)} - E^{(1)} = \left(\phi^{(2)} - \phi^{(S)} - \frac {\mu_j^{(2)}} {z_j F}\right) - \left(\phi^{(1)} - \phi^{(S)} - \frac {\mu_j^{(1)}} {z_j F}\right) = \left(\phi^{(2)} - \phi^{(1)}\right) - \left(\frac {\mu_j^{(2)} - \mu_j^{(1)}} {z_j F}\right)

where:

  • E is the potential of a single electrode,
  • (S) denotes the electrolyte solution.

From the above equation, two metals in electronic contact (i.e., under electronic equilibrium) must have the same electrode potential. Also, the electrochemical potentials of the electrons within the two metals will be the same. However, their Galvani potentials will be different (unless the metals are identical).

Read more about this topic:  Galvani Potential

Famous quotes containing the words relation to, relation, measured, cell and/or potential:

    “You must realize that I was suffering from love and I knew him as intimately as I knew my own image in a mirror. In other words, I knew him only in relation to myself.”
    —Angela Carter (1940–1992)

    “Unaware of the absurdity of it, we introduce our own petty household rules into the economy of the universe for which the life of generations, peoples, of entire planets, has no importance in relation to the general development.”
    —Alexander Herzen (1812–1870)

    “This was once
    a city among men, a gathering together of spirit.
    It was measured by the Lord and found wanting.”
    —Robert Duncan (b. 1919)

    “It is plain that there is no separate essence called courage, no cup or cell in the brain, no vessel in the heart containing drops or atoms that make or give this virtue; but it is the right or healthy state of every man, when he is free to do that which is constitutional to him to do.”
    —Ralph Waldo Emerson (1803–1882)

    “The real community of man ... is the community of those who seek the truth, of the potential knowers.”
    —Allan Bloom (1930–1992)