Question

Brine is electrolysed by using inert electrodes. The reaction at anode is ______.

Options

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

• \[\ce{2H2O (l) -> 1/2 O2 (g) + 4H^{+} + 4e^{-}; E^{Θ}_{Cell} = 1.23 V}\]

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

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

Answer 1

Brine is electrolysed by using inert electrodes. The reaction at anode is \[\ce{Cl^{-} (aq) -> 1/2 Cl2 (g) + e; E^{Θ}_{Cell} = 1.36 V}\].

Explanation:

For oxidation at anode, two possible reactions are oxidation of chlorine and of oxygen. Out of these two, oxidation of chlorine ion is preferred because oxidation of oxygen requires overvoltage.

Chlorine is obtained by electrolysis giving out hydrogen and aqueous \[\ce{NaOH}\] as byproducts.