Which of the following is not an example of homogeneous catalysis?

Options

A. Hydrolysis of esters in presence of an acid
B. Combination of `H_(2)` and `Cl_(2)` in the presence of moisture
C. Formation of sulphur trioxide in the contact process
D. Formation of sulphur trioxide in the lead chamber process

Answer

To determine which of the following is not an example of homogeneous catalysis, we need to analyze the given options based on the definition of homogeneous catalysis. Homogeneous catalysis occurs when the catalyst and the reactants are in the same phase (i.e., all are gases or all are liquids).

### Step-by-Step Solution:

1. **Identify the Options**:
- Hydrolysis of ester in the presence of acid
- Combination of H2 and Cl2
- Formation of Sulphur trioxide in the contact process
- Formation of Sulphur trioxide in the lead chamber process

2. **Analyze Each Option**:
- **Hydrolysis of Ester in Presence of Acid**:
- In this reaction, both the ester and the acid are in the liquid phase (aqueous). Therefore, this is an example of homogeneous catalysis.

- **Combination of H2 and Cl2**:
- Here, both H2 and Cl2 are gases, and they react to form HCl gas. This is also an example of homogeneous catalysis since all reactants and products are in the gas phase.

- **Formation of Sulphur Trioxide in the Contact Process**:
- In this reaction, SO2 and O2 are gases, and the product SO3 is also a gas. However, the catalyst used is solid platinum (Pt). Since the catalyst is in a different phase (solid), this is not an example of homogeneous catalysis.

- **Formation of Sulphur Trioxide in the Lead Chamber Process**:
- Similar to the contact process, SO2 and O2 are gases, and SO3 is also a gas, but the catalyst used here is nitric oxide (NO), which is also a gas. Thus, this is an example of homogeneous catalysis.

3. **Conclusion**:
- Among the options, the formation of Sulphur trioxide in the contact process is not an example of homogeneous catalysis because it involves a solid catalyst.

### Final Answer:
The formation of Sulphur trioxide in the contact process is not an example of homogeneous catalysis.