Consider the nitration of benzene using mixed `H_2SO_4` and `HNO_3`. If a larger amount of `KHSO_4` is mixture, the rate of nitration will be

Options

A. Doubled
B. Increase
C. Decrease
D. Unchanged

Explanation

To solve the problem regarding the effect of adding a larger amount of KHSO4 on the rate of nitration of benzene using mixed H2SO4 and HNO3, we can break down the process step by step:

### Step 1: Understanding the Nitration Reaction
The nitration of benzene involves the formation of the nitronium ion (NO2+), which acts as the electrophile in the electrophilic aromatic substitution reaction. The reaction occurs when benzene reacts with nitric acid (HNO3) in the presence of concentrated sulfuric acid (H2SO4).

**Hint:** Recall that the nitronium ion (NO2+) is the key electrophile in the nitration of benzene.

### Step 2: Formation of the Electrophile
In the presence of sulfuric acid, nitric acid donates a proton (H+) to form the nitronium ion (NO2+). The reaction can be summarized as follows:
- HNO3 + H2SO4 → NO2+ + HSO4- + H2O

This shows that the presence of sulfuric acid is crucial for generating the electrophile needed for the nitration.

**Hint:** Remember that sulfuric acid acts as a catalyst and helps in generating the nitronium ion from nitric acid.

### Step 3: Effect of Adding KHSO4
When KHSO4 is added to the mixture, it dissociates into K+ and HSO4-. The increase in the concentration of HSO4- ions in the solution affects the equilibrium of the reaction.

**Hint:** Consider how increasing the concentration of a product in a reversible reaction affects the equilibrium position according to Le Chatelier's principle.

### Step 4: Le Chatelier's Principle
According to Le Chatelier's principle, if the concentration of a product (in this case, HSO4-) increases, the equilibrium will shift to the left to counteract this change. This means that the formation of the nitronium ion (NO2+) will be reduced.

**Hint:** Think about how the equilibrium shifts in response to changes in concentration and how that impacts the formation of reactants and products.

### Step 5: Conclusion on the Rate of Nitration
Since the formation of the nitronium ion (NO2+) is decreased due to the increased concentration of HSO4-, the rate of nitration of benzene will also decrease. Therefore, the addition of a larger amount of KHSO4 will lead to a decrease in the rate of nitration.

**Hint:** Summarize the overall effect: increasing HSO4- concentration decreases the formation of the key electrophile, thus slowing down the reaction.

### Final Answer
The rate of nitration of benzene will decrease with the addition of a larger amount of KHSO4.