In the extraction of chlorine by electrolysis of brine_________.

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding Brine:**
- Brine is an aqueous solution of sodium chloride (NaCl). In the context of electrolysis, it is important to recognize that we are dealing with NaCl dissolved in water.

2. **Electrolysis Process:**
- During electrolysis, an electric current is passed through the brine solution, leading to chemical reactions at the electrodes. The main products of this process are chlorine gas (Cl₂), hydrogen gas (H₂), and sodium hydroxide (NaOH).

3. **Identifying the Reaction:**
- The overall reaction for the electrolysis of brine can be represented as:
\[ 2 H_2O + 2 Cl^- \rightarrow H_2 + Cl_2 + 2 OH^- \]
- Here, \(2 Cl^-\) ions (from the NaCl) are oxidized to form chlorine gas (Cl₂).

4. **Oxidation and Reduction:**
- In the reaction, the oxidation state of chlorine changes from -1 (in \(Cl^-\)) to 0 (in \(Cl_2\)). This indicates that oxidation is occurring, as the oxidation state increases.

5. **Evaluating the Options:**
- **Option 1:** "Oxidation of chloride ion to chlorine gas occurs." - This is correct, as we have established that \(Cl^-\) is oxidized to \(Cl_2\).
- **Option 2:** "Reduction of chloride ion to chlorine gas occurs." - This is incorrect because reduction would imply a decrease in oxidation state.
- **Option 3:** "For overall reaction, the standard Gibbs energy has negative value." - This is incorrect; the Gibbs energy for this reaction is positive, indicating that the reaction is non-spontaneous without external energy.
- **Option 4:** "A displacement reaction takes place." - This is incorrect as the process is primarily a redox reaction, not a displacement reaction.

6. **Conclusion:**
- The correct answer to the question is: **"Oxidation of chloride ion to chlorine gas occurs."**

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