Origln of Electrode Potential or Half Cell Potential Chemistry Notes
Origin of Electrode Potential or Half-cell Potential :
→ When a metal rod (M) remains in contact with solution of metal ion (Mn+) then one of the following process takes place in it:
→ Metal ions (Mn+) return back after colliding with metal rod without any change. Such electrode is called Null electrode.
→ Metal ions (Mn+) convert into metal atom (M) on colliding with metal rod by gaining n electrons i.e. metal ion (Mn+) gets reduced.
→ Metal (M) converts into metal ion (Mn+) by losing n electrons i.e., metal gets oxidised.
M → Mn+ + ne– (Oxidation)
→ If the nature of metal is of oxidation then metal atom loses electrons and electrons accumulate on metal rod due to which negative charge is produced on it. This negative charge attracts metal ions and balanced the charge. Due to this reason, equilibrium is established between metal ions and metal.
M ↔ Mn+ + ne–
→ If the nature of metal is of reduction these electrons are gained on metal rod from metal atom and metal ions get accumulate on rod (due to electrons) coming from solution due to which positive charge is produced on rod and here equilibrium is established.
Mn+ + ne– ↔ M
→ So, in both conditions i.e., oxidation or reduction, equilibrium is established between metal atom and metal ions. Due to this equilibrium, the separation of charge takes place between metal rod and metal ions.
→ As a result, a potential difference is produced between them which is called electrode potential “The potential difference produced between solution of metal and metal ions is called electrode potential If oxidation takes place on metal rod, then it is called oxidation potential and if reduction takes place on metal then it is called reduction potential.
The values of reduction potential and oxidation potential are same for a metal but their signs are opposite.
Oxidation potential = – Reduction potential