When halogen (except `F_2`) is passed through alkali in different conditions, the halogen undergoes

Options

A. oxidation only
B. Reduction only
C. Both oxidation and reduction
D. neither oxidation nor reduction

Answer

To solve the question regarding the reaction of halogens (except fluorine) with alkali under different conditions, we will analyze the reaction of chlorine with hot and concentrated sodium hydroxide (NaOH) solution as an example.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The halogen we will consider is chlorine (Cl₂).
- The alkali is sodium hydroxide (NaOH), which we will use in a hot and concentrated form.

2. **Write the Reaction**:
- When chlorine gas is passed through hot and concentrated sodium hydroxide, the reaction can be represented as:
\[ Cl_2 + 2 NaOH \rightarrow NaCl + NaClO + H_2O \]
- Here, sodium chloride (NaCl) and sodium hypochlorite (NaClO) are formed along with water (H₂O).

3. **Determine the Oxidation States**:
- In the elemental state (Cl₂), the oxidation number of chlorine is 0.
- In sodium chloride (NaCl), the oxidation number of chlorine is -1.
- In sodium hypochlorite (NaClO), the oxidation number of chlorine is +1.

4. **Analyze the Changes in Oxidation States**:
- From Cl₂ (0) to NaCl (-1): This indicates a **reduction** (decrease in oxidation state).
- From Cl₂ (0) to NaClO (+1): This indicates an **oxidation** (increase in oxidation state).

5. **Conclusion**:
- Since both oxidation and reduction processes occur during the reaction, we conclude that when halogens (except fluorine) are passed through alkali under certain conditions, both oxidation and reduction take place.

### Final Answer:
The correct answer is that both oxidation and reduction occur when halogens (except fluorine) are passed through alkali.

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