Acid catalysed hydrolysis of ethyl acetate follows a pseudo-first order kinetics with respect to ester . If the reaction is carried out with large excess of ester , the order with respect to ester will be

Options

A. 1.5
B. 0
C. 2
D. 1

Explanation

To solve the problem regarding the order of the acid-catalyzed hydrolysis of ethyl acetate when carried out with a large excess of ester, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The hydrolysis of ethyl acetate (C2H5COOCH3) can be represented as:
\[ C2H5COOCH3 + H2O \xrightarrow{H^+} CH3COOH + C2H5OH \]
Here, ethyl acetate reacts with water in the presence of an acid catalyst to produce acetic acid and ethanol.

2. **Identifying the Kinetics**:
The problem states that the reaction follows pseudo-first-order kinetics with respect to the ester (ethyl acetate). This means that the concentration of water is in large excess, making the reaction appear to depend only on the concentration of the ester.

3. **Rate Law Expression**:
The rate law for this reaction can be expressed as:
\[ R = k [\text{Ester}]^1 [\text{Water}]^0 \]
Since water is in excess, we can consider its concentration to be constant. Therefore, the rate can be simplified to:
\[ R = k' [\text{Ester}]^1 \]
where \( k' = k[\text{Water}]^0 \) is a new rate constant.

4. **Effect of Large Excess of Ester**:
If the concentration of the ester is very high (large excess), we can assume that its concentration does not change significantly during the reaction. This means that the concentration of the ester can be treated as a constant.

5. **Revising the Rate Expression**:
When the concentration of the ester is treated as constant, the rate expression can be simplified further:
\[ R = k' \quad \text{(where } k' \text{ is a new constant)} \]
This indicates that the rate of the reaction is independent of the concentration of the ester.

6. **Determining the Order with Respect to Ester**:
Since the rate is now independent of the concentration of the ester, we conclude that the reaction behaves as zero-order with respect to the ester when it is in large excess.

### Final Answer:
The order with respect to ester when the reaction is carried out with a large excess of ester will be **zero order**.

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