In a thermite reaction, a compound of iron reacts with a metal.
The metal used is:

Options

A. Zinc
B. Aluminium
C. Magnesium
D. None of these.

Explanation

To solve the question about the metal used in a thermite reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Thermite Reaction**:
The thermite reaction involves a compound of iron, typically iron(III) oxide (Fe2O3), reacting with a more reactive metal to produce molten iron and aluminum oxide (Al2O3).

2. **Identifying the Reactive Metal**:
In the thermite reaction, the metal that is commonly used is aluminum (Al). Aluminum is chosen because it is more reactive than iron and can displace iron from its compound.

3. **Reaction Equation**:
The thermite reaction can be represented by the following chemical equation:
\[ Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3 \]
This shows that aluminum reacts with iron(III) oxide to produce iron in a molten state and aluminum oxide.

4. **Exothermic Nature of the Reaction**:
The reaction is highly exothermic, meaning it releases a significant amount of heat, which is why the iron produced is in a molten state.

5. **Applications of the Thermite Reaction**:
The molten iron produced is used to fill cracks in railway tracks, as it can take the shape of the cracks and solidify, providing a strong repair.

6. **Conclusion**:
Based on the understanding of the thermite reaction and the metals involved, we conclude that the metal used in the reaction with iron is aluminum.

### Final Answer:
The metal used in a thermite reaction is **Aluminum (Al)**.

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