Electroanalytical Chemistry Lecture 4 Why Electrons Transfer
Electroanalytical Chemistry Lecture #4 Why Electrons Transfer?
The metal electrode Ef= Fermi level highest occupied electronIc energy level in a metal E
The Metal Electrode EF E Ef = Fermi level; highest occupied electronic energy level in a metal
Why Electrons Transfer Reduction Oxidation F E redox E E redox E F .Net flow of electrons from m.Net flow of electrons from to solute solute to m Ef more negative than e E redox f more positive than ered emore cathodic emore anodic g emore reducin more oxidizing
Why Electrons Transfer EF Eredox E F Eredox •Net flow of electrons from M to solute •Ef more negative than Eredox •more cathodic •more reducing Reduction Oxidation •Net flow of electrons from solute to M •Ef more positive than Eredox •more anodic •more oxidizing E E
The inetics of electron Transfer Consider 0+ne=R Assume o andr are stable soluble Electrode of 3rd kind (i.e inert no competing chemical reactions occur
The Kinetics of Electron Transfer Consider: O + ne- = R Assume: O and R are stable, soluble Electrode of 3rd kind (i.e., inert) no competing chemical reactions occur kR ko
Equilibrium for this Reaction is Characterised byu The nernst equation Ecell Eo-(rt/nF)In(Cr co) where R=[R] in bulk solution Co *=OJ in bulk solution So, Ecell is related directly to [o] and [r]
Equilibrium for this Reaction is Characterised by... The Nernst equation: Ecell = E0 - (RT/nF) ln (cR * /co * ) where: cR * = [R] in bulk solution co * = [O] in bulk solution So, Ecell is related directly to [O] and [R]