Which of the following processes does not occur at the interface of phases?

Options

A. Crystallisation
B. Hetergeneous catalysis
C. Homogeneous catalysis
D. Corrosion

Explanation

To determine which process does not occur at the interface of phases, we will analyze each of the given options step by step.

### Step 1: Understand the Concept of Interface of Phases
The interface of phases refers to the boundary where two different phases (solid, liquid, gas) interact. For example, the interface can exist between a solid and a liquid, a solid and a gas, or a liquid and a gas.

### Step 2: Analyze Each Option

1. **Crystallization**:
- Crystallization involves the transition of solute from a dissolved state in a liquid to a solid state.
- This process occurs at the interface between the liquid phase (solution) and the solid phase (crystals).
- **Conclusion**: Crystallization occurs at the interface of phases.

2. **Heterogeneous Catalysis**:
- In heterogeneous catalysis, the catalyst and the reactants are in different phases (e.g., a solid catalyst facilitating a reaction with gaseous reactants).
- The reaction occurs at the surface of the solid catalyst where the gas molecules adsorb, creating an interface.
- **Conclusion**: Heterogeneous catalysis occurs at the interface of phases.

3. **Homogeneous Catalysis**:
- In homogeneous catalysis, both the catalyst and the reactants are in the same phase (e.g., both in a liquid phase).
- Since there is no distinct boundary between different phases, there is no interface formed.
- **Conclusion**: Homogeneous catalysis does not occur at the interface of phases.

4. **Corrosion**:
- Corrosion typically involves the reaction of a solid (metal) with a gas (like oxygen) or a liquid (like water).
- This process creates an interface between the solid metal and the gas or liquid.
- **Conclusion**: Corrosion occurs at the interface of phases.

### Step 3: Final Conclusion
After analyzing all the options, we find that the process that does not occur at the interface of phases is **Homogeneous Catalysis**.

### Answer:
**Option 3: Homogeneous Catalysis**

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