In the Haber’s process of synthesis of `NH_3`

Options

A. Mo acts as a catalyst and Fe as a promoter
B. Fe acts as a catalyst and Mo as a promoter
C. Fe acts as inhibitor and Mo as a catalyst
D. Fe acts as promoter and Mo as auto catalyst

Answer

To solve the question regarding the Haber process for the synthesis of ammonia (NH₃), we need to analyze the roles of iron and molybdenum in this chemical reaction.

### Step-by-step Solution:

1. **Understanding the Haber Process**:
The Haber process is a method used to synthesize ammonia from nitrogen and hydrogen gases. The balanced chemical equation for the reaction is:
\[ N_2(g) + 3H_2(g) \rightarrow 2NH_3(g) \]

2. **Identifying the Catalyst**:
In the Haber process, iron (Fe) is commonly used as a catalyst. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

3. **Identifying the Promoter**:
Molybdenum (Mo) acts as a promoter in the Haber process. A promoter is a substance that enhances the effectiveness of a catalyst but is not a catalyst itself.

4. **Analyzing the Options**:
- **Option 1**: Molybdenum acts as a catalyst and iron as a promoter. (Incorrect)
- **Option 2**: Iron acts as a catalyst and molybdenum as a promoter. (Correct)
- **Option 3**: Iron acts as an inhibitor and molybdenum as a catalyst. (Incorrect)
- **Option 4**: Iron acts as a promoter and molybdenum as an autocatalyst. (Incorrect)

5. **Conclusion**:
Based on the roles of iron and molybdenum in the Haber process, the correct answer is:
**Option 2: Iron acts as a catalyst and molybdenum as a promoter.**