Electrochemical Systems

Electrochemical systems involve an electric potential difference, ΔΦ, between two or more phases.

For instance, when zinc metal is immersed in a dilute zinc sulfate solution, the low concentration of Zn²⁺ ions drives zinc atoms to dissolve into the solution, leaving electrons behind in the metal, resulting in a net negative charge on the zinc.

This dynamic process at equilibrium establishes a potential difference between the zinc and the solution, and these moving ions carrying charge form an exchange current.

The number of moles of ions carrying this charge can be determined using the Faraday constant, which is the charge per mole of electrons.

So, the charge on n_i moles of species i is the product of the charge number, the Faraday constant, and n_i.

The magnitude and sign of ΔΦ depend on factors like temperature, pressure, the nature of the metal, the solvent, and ion concentrations.

Similarly, electron movement between metals like copper and zinc can create a net charge at equilibrium, a phenomenon used in thermocouples, which measure temperature through interphase potential differences.

Measurement of ΔΦ is viable only between phases that are in equilibrium.