ELECTRODE POTENTIAL AND STANDARD ELECTRODE POTENTIALS
- Electrons will flow from the electrode of higher negative charge density to the electrode with lower negative electric charge density.
- A property closely related to the density of negative electric charge is called the electrode potential.
- 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:
\(\overset{Half\,Cell}{\mathop{Zn|Z{{n}^{2+}}(aq)}}\,\,\,\,\,\,\overset{\operatorname{Re}action}{\mathop{Zn\to Z{{n}^{2+}}(aq)}}\,\,\,\,\,\,\underset{\underset{In\,the\,s\tan dard\,state}{\mathop{E_{OX}^{0}(or)E_{Zn|Z{{n}^{2+}}}^{0}}}\,}{\mathop{\underset{\operatorname{Re}presents\,\,\,oxidation\,electrode\,potential\,in\,the\,given\,state}{\overset{Electrode\,Potential}{\mathop{{{E}_{OX}}(or){{E}_{Zn|Z{{n}^{2+}}}}}}}\,}}\,\) \(C{{u}^{2+}}(aq)\,|Cu\,\,C{{u}^{2+}}(aq)\,+\,2{{e}^{-}}\to Cu\,\,\,\underset{\underset{In\,the\,\,standard\,\,state}{\mathop{E_{red}^{0}(or)E_{C{{u}^{2+}}}^{0}|Cu}}\,}{\mathop{\underset{\operatorname{Re}presents\,\,reduction\,electrode\,potential\,in\,the\,given\,state}{\mathop{{{E}_{red}}(or){{E}_{C{{u}^{2+}}|Cu}}}}\,}}\,\)- E°Cl¯|Pt(Cl₂) is a standard electrode potential of the half-cell Cl¯(aq)|Pt(Cl₂)
- E°AgCl|Cl¯(aq) is the standard oxidation potential of the half–cell Ag, AgCl|(-)Cl¯(aq)
- E°cell (or) Ecell is the potential difference between the two half cells
- E°cell = E°OX + E°red
- Ecell = EOX + Ered
- If E°OX = xV then E°red = – xV
- E°Cu²⁺|Cu = 0.34V then E° Cu|Cu²⁺ = – 0.34V
- E°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.