Redox potential and pe
pe = −log{e−}, where {e−}
is the activity of electrons.
This variable is used because of its similarity with pH.
But e− is not an aqueous species,
in contrast to H+.
The activity of electrons may be interpreted to represent the relative
tendency for a given dissolved oxidant to accept electrons,
or for electrons to leave the electrode in a galvanic cell.
pe is related to the redox potential, ESHE:
|
pe = ESHE F / (R T ln(10))
|
where F and
R are the Faraday and gas constants,
and T is the temperature in degrees Kelvin (2.303 R T
/ F = 0.059 V at 25°C).
ESHE
is the potential that a platinum electrode would ideally have in contact with
the aqueous solution when measured against a standard hydrogen electrode (SHE).
Sometimes it is referred as Eh (instead of ESHE).