Why is an external emf of more than `2.2V` required for the extraction of `CI_(2)` from brine?

Explanation

To understand why an external emf of more than 2.2V is required for the extraction of Cl2 from brine, we can break down the process step by step.

### Step 1: Understand the Reaction
The extraction of chlorine from brine involves the electrolysis of brine (a concentrated solution of sodium chloride). The relevant half-reaction for the extraction of chlorine gas (Cl2) can be represented as:
\[ \text{Cl}^- + 2\text{H}_2\text{O} \rightarrow \text{OH}^- + \text{H}_2 + \text{Cl}_2 \]

### Step 2: Calculate the Gibbs Free Energy Change
The Gibbs free energy change (ΔG°) for this reaction is found to be +422 kJ. This positive value indicates that the reaction is non-spontaneous under standard conditions.
...