Question

The cell reaction occurring at anode in the electrolysis of aqueous NaCl solution is:

• A. \[ \text{H}^+ (aq) + e^- \rightarrow \frac{1}{2} \text{H}_2(g), E^\circ_\text{cell} = 0.00 V \]
• B. \[ \text{Cl}^- (aq) \rightarrow \frac{1}{2} \text{Cl}_2(g) + e^-, E^\circ_\text{cell} = 1.36 V \]
• C. \[ \text{Na}^+ (aq) + e^- \rightarrow \text{Na}(s), E^\circ_\text{cell} = -2.71 V \]
• D. \[ 2 \text{H}_2\text{O}(l) \rightarrow \text{O}_2(g) + 4 \text{H}^+(aq) + 4e^-, E^\circ_\text{cell} = -1.23 V \]

Hint:

At the anode during the electrolysis of aqueous NaCl, water is oxidized to produce oxygen gas, not chloride ions, because of the higher oxidation potential of water.

Answer 1

The Correct Option is D

In the electrolysis of aqueous NaCl solution, the anode is where oxidation occurs. In the case of NaCl electrolysis, the species that undergoes oxidation at the anode is water (H₂O), not chloride ions (Cl⁻), due to the lower oxidation potential of chloride ions compared to water.
Thus, oxygen gas is produced at the anode. - The relevant half-reaction for oxidation at the anode is the oxidation of water: \[ 2 \text{H}_2\text{O}(l) \rightarrow \text{O}_2(g) + 4 \text{H}^+(aq) + 4e^-, \, E^\circ_\text{cell} = -1.23 \, V \] - Chloride ions (Cl⁻), while present, are not oxidized at the anode because the oxidation potential for chloride is less favorable than that of water.
Therefore, oxygen is the product at the anode.
Thus, the correct cell reaction occurring at the anode in the electrolysis of aqueous NaCl solution is: \[ 2 \text{H}_2\text{O}(l) \rightarrow \text{O}_2(g) + 4 \text{H}^+(aq) + 4e^-, \, E^\circ_\text{cell} = -1.23 \, V \]