Electrode Potential and Standard Electrode Potentials


  1. Electrons will flow from the electrode of higher negative charge density to the electrode with lower negative electric charge density.
  2. A property closely related to the density of negative electric charge is called the electrode potential.
  3. Potential difference between the metal and metal ion in which electrode is dipped is called electrode potential.

Standard electrode potentials: In standard state, i.e., when pressure is 1 atm and concentration is 1M, the electrode potential is called standard electrode potential denoted as E°. Temperature is generally taken as 298 K

For example:

\(\overset{Half\,Cell}{\mathop{Zn|Z{{n}^{2+}}(aq)}}\,\,\,\,\,\,\overset{\operatorname{Re}action}{\mathop{Zn\to Z{{n}^{2+}}(aq)}}\,\,\,\,\,\,\underset{\underset{In\,the\,s\tan dard\,state}{\mathop{E_{OX}^{0}(or)E_{Zn|Z{{n}^{2+}}}^{0}}}\,}{\mathop{\underset{\operatorname{Re}presents\,\,\,oxidation\,electrode\,potential\,in\,the\,given\,state}{\overset{Electrode\,Potential}{\mathop{{{E}_{OX}}(or){{E}_{Zn|Z{{n}^{2+}}}}}}}\,}}\,\) \(C{{u}^{2+}}(aq)\,|Cu\,\,C{{u}^{2+}}(aq)\,+\,2{{e}^{-}}\to Cu\,\,\,\underset{\underset{In\,the\,\,standard\,\,state}{\mathop{E_{red}^{0}(or)E_{C{{u}^{2+}}}^{0}|Cu}}\,}{\mathop{\underset{\operatorname{Re}presents\,\,reduction\,electrode\,potential\,in\,the\,given\,state}{\mathop{{{E}_{red}}(or){{E}_{C{{u}^{2+}}|Cu}}}}\,}}\,\)
  • Cl¯|Pt(Cl₂) is a standard electrode potential of the half-cell Cl¯(aq)|Pt(Cl₂)
  • AgCl|Cl¯(aq) is the standard oxidation potential of the half–cell Ag, AgCl|(-)Cl¯(aq)
  • cell (or) Ecell is the potential difference between the two half cells
  • cell = E°OX + E°red
  • Ecell = EOX + Ered
  • If E°OX = xV then E°red = – xV
  • Cu²⁺|Cu = 0.34V then E° Cu|Cu²⁺ = – 0.34V
  • cell = E°right – E°left

Note: Both these E°right and E°left are reduction potentials of right hand side (cathode) and left hand side (anode) half–cells respectively.