In the extraction of chlorine by electrolysis of brine_________.

Options

A. oxidation of `Cl^(-)` ion to chlorine gas occurs
B. reduction of `Cl^(-)` ion to chlorine gas occurs
C. for overall reaction `DeltaG^(@)` has negative value
D. a displacement reaction takes place

Answer

To solve the question regarding the extraction of chlorine by electrolysis of brine, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Process**: The extraction of chlorine occurs through the electrolysis of brine, which is a concentrated solution of sodium chloride (NaCl) in water.

2. **Writing the Electrolysis Reaction**: The electrolysis of brine can be represented by the following half-reaction:
\[ 2 \text{Cl}^- (aq) + 2 \text{H}_2\text{O} (l) \rightarrow 2 \text{OH}^- (aq) + \text{H}_2 (g) + \text{Cl}_2 (g) \]
In this reaction, chloride ions (Cl^-) are oxidized to chlorine gas (Cl2).

3. **Identifying Oxidation and Reduction**: In the reaction, the oxidation state of chlorine changes from -1 in Cl^- to 0 in Cl2. This indicates that the chloride ions are being oxidized.

4. **Calculating Gibbs Free Energy Change (ΔG°)**: The standard Gibbs free energy change (ΔG°) for this reaction is given as +422 kJ. A positive ΔG° indicates that the reaction is non-spontaneous under standard conditions.

5. **Analyzing the Options**:
- **Option A**: "Oxidation of chloride ion to chlorine gas occurs" - This is correct because Cl^- is oxidized to Cl2.
- **Option B**: "Reduction of chloride ion to chlorine gas occurs" - This is incorrect; it is an oxidation process, not reduction.
- **Option C**: "For overall reaction ΔG° value has a negative value" - This is incorrect; ΔG° is positive.
- **Option D**: "The given reaction is a displacement reaction" - This is incorrect; it is an oxidation-reduction reaction.

6. **Conclusion**: The correct answer is Option A, which states that the oxidation of chloride ion to chlorine gas occurs.