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:

    “The proper study of mankind is man in his relation to his deity.”
    —D.H. (David Herbert)

    “Concord is just as idiotic as ever in relation to the spirits and their knockings. Most people here believe in a spiritual world ... in spirits which the very bullfrogs in our meadows would blackball. Their evil genius is seeing how low it can degrade them. The hooting of owls, the croaking of frogs, is celestial wisdom in comparison.”
    —Henry David Thoreau (1817–1862)

    “I must remind you that our credulity is not to be measured by the truth of the things we believe. When men believed that the earth was flat, they were not credulous: they were using their common sense, and, if asked to prove that the earth was flat, would have said simply, “Look at it.” Those who refuse to believe that it is round are exercising a wholesome skepticism.”
    —George Bernard Shaw (1856–1950)

    “Let man consider what he is in comparison with all existence; let him regard himself as lost in this remote corner of nature; and from the little cell in which he finds himself lodged, I mean the universe, let him estimate at their true value the earth, kingdoms, cities, and himself. What is a man in the infinite?”
    —Blaise Pascal (1623–1662)

    “Much of what contrives to create critical moments in parenting stems from a fundamental misunderstanding as to what the child is capable of at any given age. If a parent misjudges a child’s limitations as well as his own abilities, the potential exists for unreasonable expectations, frustration, disappointment and an unrealistic belief that what the child really needs is to be punished.”
    —Lawrence Balter (20th century)