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Electrolysis of NaCl (aq) is carried out using inert electrodes, choose the correct option(s):

A
When concentrated NaCl is used, oxygen gas is liberated at anode.
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B
When dilute NaCl is used, chlorine gas is liberated at anode.
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C
When concentrated NaCl is used, chlorine gas is liberated at anode.
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D
When dilute NaCl is used, oxygen gas is liberated at anode.
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Solution

The correct option is D When dilute NaCl is used, oxygen gas is liberated at anode.
Electrolysis of concentrated NaCl (aq) carried out using inert electrodes:

Since ,
E0H2O/H2>E0Na+/Na

Reaction at cathode:
2H2O(l)+2eH2(g)+2OH(aq)

Reaction at anode:
Even if E0Cl/Cl2<E0H2O/O2
Kinetically rate of oxidation of water is very slow. To increase its rate, the greater potential difference is applied called as overpotential.Because of this overpotential, oxidation of Cl ions becomes more feasible
The reaction that occurs at anode is :
2ClCl2(g)+2e
So, chroine gas is involved at anode.

Electrolysis of dilute NaCl (aq) carried out using inert electrodes:

Since ,
E0H2O/H2>E0Na+/Na

Reaction at cathode:
2H2O(l)+2eH2(g)+2OH(aq)

Reaction at anode: If concentration of Cl is low, oxidation of H2O to give O2 is favoured.

2H2O(l)4H+(aq)+O2(g)+4e

When dilute NaCl is used, oxygen gas is liberated at anode.

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