Iron is used as a catalyst in the manufacture of ammonia. It is an example of

Options

A. heterogeneous catalysis
B. homogeneous catalysis
C. autocatalysis
D. induced catalysis

Explanation

To solve the question regarding the use of iron as a catalyst in the manufacture of ammonia, we can follow these steps:

### Step 1: Understand the Reaction
The synthesis of ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) can be represented by the following equation:
\[ N_2(g) + 3H_2(g) \rightarrow 2NH_3(g) \]
Here, both nitrogen and hydrogen are in the gaseous state.

### Step 2: Identify the Role of Iron
In this reaction, iron (Fe) is used as a catalyst. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

### Step 3: Determine the Phase of the Catalyst
Iron is a solid at room temperature. Therefore, in the context of this reaction:
- Reactants (N₂ and H₂) are in the gas phase.
- Catalyst (Fe) is in the solid phase.

### Step 4: Classify the Type of Catalyst
Based on the phases of the reactants and the catalyst:
- A **heterogeneous catalyst** is one where the catalyst and the reactants are in different phases.
- A **homogeneous catalyst** is one where the catalyst and the reactants are in the same phase.

Since iron (solid) and the reactants (gases) are in different phases, iron is classified as a **heterogeneous catalyst**.

### Conclusion
Thus, the correct answer to the question is that iron is an example of a **heterogeneous catalyst**.

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