Nitrobenzenen can be prepared from benzene by using a mixture of conc `HNO_(3)` and conc. `H_(2)SO_(4)` in the nitrating mixture. Nitric acid acts as a

Options

A. catalyst
B. reducing agent
C. acid
D. base

Explanation

To determine the role of nitric acid in the preparation of nitrobenzene from benzene using concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: The reaction involves the nitration of benzene, where benzene (C6H6) reacts with a nitrating mixture of concentrated HNO3 and H2SO4 to form nitrobenzene (C6H5NO2).

2. **Write the Chemical Equation**:
\[ C_6H_6 + HNO_3 \xrightarrow{H_2SO_4} C_6H_5NO_2 + H_2O \]
Here, benzene reacts with nitric acid in the presence of sulfuric acid to produce nitrobenzene and water.

3. **Understand the Role of Reagents**:
- **Sulfuric Acid (H2SO4)**: Acts as a dehydrating agent. It helps in generating the nitronium ion (NO2^+) from nitric acid by removing a water molecule.
- **Nitric Acid (HNO3)**: It provides the nitronium ion (NO2^+) which is the active electrophile in the reaction.

4. **Formation of the Electrophile**:
The reaction between nitric acid and sulfuric acid can be illustrated as follows:
\[ HNO_3 + H_2SO_4 \rightarrow NO_2^+ + HSO_4^- + H_2O \]
In this step, sulfuric acid donates a proton (H^+) to nitric acid, facilitating the formation of the nitronium ion (NO2^+), which is essential for the nitration process.

5. **Determine the Role of Nitric Acid**:
In this context, nitric acid acts as a base because it accepts a proton (H^+) from sulfuric acid. This is a key point in understanding its role in the reaction.

6. **Conclusion**:
Based on the above steps, we conclude that nitric acid acts as a base in the nitration of benzene to form nitrobenzene.

### Final Answer:
Nitric acid acts as a **base** in the nitration reaction.

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