during the electrolysis of aqueous NaCl at anode following rxns may takes place: cl(-) gives 1/2Cl2 + e(-) E(0)=1.36V or 2H2O gives O2 + 4H(+) + 4e(-) E(0)=1.23V the rxn at anode with lower potential shud be preferred and thus water shud get oxidised in preference to cl(-).however on account of overpotential of oxygen rxn of Cl(-) is preferred. WHAT THIS OVERPOTENTIAL REFERS HERE AND WHAT IS ITS SIGNIFICANCE IN THE REDOX RXNS. ALSO EXPLAIN THE MECHANISM OF THE OXIDATION OF H20 AS SHOWN ABOVE IN THE RXN

Asked by puneeta budhwar | 2nd Jan, 2013, 07:13: PM

Expert Answer:

Overpotential here is referring to the potential difference or voltage) between a half-reaction reduction potential and the potential at which the redox reaction is experimentally observed.

In redox reactions, there can be four possible polarities of overpotentials which are listed below.

Due to overpotential:

  • An electrolytic cell's anode is more positive which means it uses more energy than its thermodynamics require.
  • An electrolytic cell's cathode is more negative which signifies it uses more energy than thermodynamics require.
  • A galvanic cell's anode is less negative which means it supplies less energy than thermodynamically possible.
  • A galvanic cell's cathode is less positive which means it supplies less energy than thermodynamically possible.

Answered by  | 3rd Jan, 2013, 01:17: PM

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