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Karnataka Board PUCPUC Science 2nd PUC Class 12

In the electrolysis of aqueous sodium chloride solution which of the half cell reaction will occur at anode?

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Question

In the electrolysis of aqueous sodium chloride solution which of the half cell reaction will occur at anode?

Options

  • \[\ce{Na+ (aq) + e- -> Na (s); E^{Θ}_{cell} = - 2.71V}\]

  • \[\ce{2H2O (l) -> O2(g) + 4H+ (aq) + 4e^- ; E^{Θ}_{cell} = 1.23V}\]

  • \[\ce{H^+ (aq) + e^- -> 1/2 H2 (g); E^{Θ}_{cell} = 0.00V}\]

  • \[\ce{Cl^- (aq) -> 1/2 Cl2 (g) + e^- ; E^{Θ}_{cell} = 1.36V}\]

MCQ
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Solution

\[\ce{Cl^- (aq) -> 1/2 Cl2 (g) + e^- ; E^{Θ}_{cell} = 1.36V}\]

Explanation:

During electrolysis of aqueous

\[\ce{NaCl -> Na^+ + Cl^-}\]

\[\ce{H2O -> H+ + OH-}\]

\[\ce{Na+ + e- -> Na (E^{Θ}_{cell} = - 2.71V)}\]

\[\ce{H^+ e- -> 1/2 H2 E^{Θ}_{cell} = 0.00V}\]

At cathode,

\[\ce{H2O + e- -> 1/2 H2 + OH-}\]

At anode, two reactions are possible.

\[\ce{Cl^{-} -> 1/2 Cl2 + e- ; E^{Θ}_{cell} = 1.36V}\]

\[\ce{2H2O -> O2 + 4H+ + 4e- ; E^{Θ}_{cell} = 1.23V}\]

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Chapter 3: Electrochemistry - Exercises [Page 36]

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NCERT Exemplar Chemistry Exemplar [English] Class 12
Chapter 3 Electrochemistry
Exercises | Q I. 17. | Page 36

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