Consider the nitration of benzene using mixed conc. `H_(2)SO_(4)` and `HNO_(3)`. If a large amount of `KHSO_(4)` is added to the mixture, the rate of nitration will be `:`
(a)slower
(b)unchanged
(c)doubled
(d)faster

Options

A. slower
B. unchanged
C. doubled
D. faster

Explanation

To solve the question regarding the effect of adding a large amount of potassium hydrogen sulfate (KHSO₄) on the rate of nitration of benzene using a mixture of concentrated sulfuric acid (H₂SO₄) and nitric acid (HNO₃), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Nitration Process**:
- The nitration of benzene involves the generation of the nitronium ion (NO₂⁺), which is the electrophile responsible for the reaction. This ion is formed from nitric acid in the presence of sulfuric acid.
- The overall reaction can be represented as:
\[ \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NO}_2^+ + \text{HSO}_4^- + \text{H}_2\text{O} \]

2. **Effect of Adding KHSO₄**:
- When a large amount of KHSO₄ is added to the mixture, it dissociates to provide additional hydrogen sulfate ions (HSO₄⁻).
- The presence of more HSO₄⁻ ions affects the equilibrium of the reaction that generates the nitronium ion (NO₂⁺).

3. **Decrease in Electrophile Concentration**:
- The increase in HSO₄⁻ ions leads to a shift in the equilibrium, resulting in a decrease in the concentration of the nitronium ion (NO₂⁺).
- Since the rate of the nitration reaction is directly proportional to the concentration of the electrophile (NO₂⁺), a decrease in its concentration will lead to a slower reaction rate.

4. **Conclusion**:
- Therefore, the addition of a large amount of KHSO₄ will result in a slower rate of nitration of benzene.

### Final Answer:
The rate of nitration will be **(a) slower**.