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 adolescent does not develop her identity and individuality by moving outside her family. She is not triggered by some magic unconscious dynamic whereby she rejects her family in favour of her peers or of a larger society.... She continues to develop in relation to her parents. Her mother continues to have more influence over her than either her father or her friends.”
    —Terri Apter (20th century)

    “Whoever has a keen eye for profits, is blind in relation to his craft.”
    —Sophocles (497–406/5 B.C.)

    “Rather would I have the love songs of romantic ages, rather Don Juan and Madame Venus, rather an elopement by ladder and rope on a moonlight night, followed by the father’s curse, mother’s moans, and the moral comments of neighbors, than correctness and propriety measured by yardsticks.”
    —Emma Goldman (1869–1940)

    “Women have no wilderness in them,
    They are provident instead,
    Content in the tight hot cell of their hearts
    To eat dusty bread.”
    —Louise Bogan (1897–1970)

    “A child is born with the potential ability to learn Chinese or Swahili, play a kazoo, climb a tree, make a strudel or a birdhouse, take pleasure in finding the coordinates of a star. Genetic inheritance determines a child’s abilities and weaknesses. But those who raise a child call forth from that matrix the traits and talents they consider important.”
    —Emilie Buchwald (20th century)