Which one of the following is wrongly matched?

Options

A. Saponification of `CH_(3COOC_(2)H_(5)` - second order reaction
B. Hydrolysis of `CH_(3)COOCH_(3)` - Pseudounimolecular reaction
C. Decomposition of `H_(2)O_(2)` - First order reaction
D. Combination of `H_(2)` and `Br_(2)` to give HBr - Zero order reaction

Answer

To determine which option is wrongly matched in the question, we will analyze each reaction and its corresponding order.

### Step 1: Analyze the first option
**Option 1:** Saponification of CH3COOC2H5 is a second-order reaction.

- Saponification is a reaction between an ester (in this case, ethyl acetate, CH3COOC2H5) and a base (usually NaOH) to produce an alcohol and a carboxylic acid.
- The rate of this reaction depends on the concentration of both the ester and the base, which makes it a second-order reaction.

**Conclusion:** This option is correctly matched.

### Step 2: Analyze the second option
**Option 2:** Hydrolysis of CH3COOCH3 is a pseudounimolecular reaction.

- Hydrolysis of methyl acetate (CH3COOCH3) involves its reaction with water.
- In dilute conditions, the concentration of water remains essentially constant, making the reaction appear to be first-order with respect to the ester only, hence it is termed pseudounimolecular.

**Conclusion:** This option is correctly matched.

### Step 3: Analyze the third option
**Option 3:** Decomposition of H2O2 is a first-order reaction.

- The decomposition of hydrogen peroxide (H2O2) is known to follow first-order kinetics under certain conditions, where the rate of reaction depends on the concentration of H2O2 alone.

**Conclusion:** This option is correctly matched.

### Step 4: Analyze the fourth option
**Option 4:** Combination of H2 and Br2 to give HBr is a zero-order reaction.

- The reaction between hydrogen (H2) and bromine (Br2) to form hydrogen bromide (HBr) can be represented as:
\[ H_2 + Br_2 \rightarrow 2 HBr \]
- The rate of this reaction depends on the concentrations of both H2 and Br2.
- Therefore, the overall order of the reaction is 1 (for H2) + 1 (for Br2) = 2, indicating that it is a second-order reaction, not a zero-order reaction.

**Conclusion:** This option is wrongly matched.

### Final Answer
The wrongly matched option is **Option 4**: Combination of H2 and Br2 to give HBr is a zero-order reaction.

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