Question

The atomic radius of C and Fe are 77 pm and 126 pm respectively. Which statement regarding the formation of an alloy is correct?

A. Carbon forms an interstitial alloy with iron because their radii are about the same
B. Carbon forms a substitutional alloy with iron because their radii are about the same
C. Carbon forms an interstitial alloy with iron because carbon has a much smaller atomic radius
D. Carbon forms a substitutional alloy with iron because carbon has a much smaller atomic radius
E. Carbon forms an interstitial alloy with iron because carbon has a much larger atomic radius

Answer 1

The correct answer is option c).Carbon forms an interstitial alloy with iron because carbon has a much smaller atomic radius than iron.

Step-by-step explanation:

An interstitial alloy is formed when smaller atoms fit in between the larger atoms in the crystal packing arrangement. A substitutional alloy is formed when atoms simply replace each other in the crystal structure.

In this case, carbon forms an interstitial alloy with iron because carbon has a much smaller atomic radius than iron. The atomic radius of carbon is 77 pm, while the atomic radius of iron is 126 pm. Since the atomic radii of carbon and iron are significantly different, carbon would not fit into the crystal structure of iron atoms and replace them, making option B incorrect.