Which one of the following is the correct statement ?

Options

A. Brass is an interstitial alloy , while steel is a substitutional alloy
B. Brass is a substitutional alloy, while steel is an interstitial alloy
C. Brass and steel are both substitutional alloys
D. Brass and steel are both interstitial alloys

Answer

To determine which statement about brass and steel is correct, we need to understand the definitions and characteristics of interstitial and substitutional alloys.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Interstitial Alloys**: These are formed when the atoms of one element are significantly smaller than those of the other element, allowing the smaller atoms to fit into the spaces (interstices) between the larger atoms. A common example of an interstitial alloy is steel, which is primarily iron with carbon atoms filling the interstitial spaces.
- **Substitutional Alloys**: These are formed when the atoms of the two elements are of similar sizes, allowing one type of atom to substitute for the other in the crystal lattice. Brass, which is an alloy of copper and zinc, is an example of a substitutional alloy.

2. **Analyze Each Statement**:
- **Statement 1**: "Brass is an interstitial alloy, while steel is a substitutional alloy."
- This is incorrect because brass is a substitutional alloy and steel is an interstitial alloy.
- **Statement 2**: "Brass is a substitutional alloy, while steel is an interstitial alloy."
- This is correct as it accurately describes the nature of both alloys.
- **Statement 3**: "Brass and steel both are substitutional alloys."
- This is incorrect because steel is not a substitutional alloy; it is an interstitial alloy.
- **Statement 4**: "Brass and steel are both interstitial alloys."
- This is incorrect for the same reason as Statement 3; brass is not an interstitial alloy.

3. **Conclusion**:
- The only correct statement is **Statement 2**: "Brass is a substitutional alloy, while steel is an interstitial alloy."

### Final Answer:
The correct statement is **Statement 2**.

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