Problem 41 - Chemistry: The Central Science

Question

Indicate whether each statement is true or false: (a) Substitutional alloys tend to be more ductile than interstitial alloys. (b) Interstitial alloys tend to form between elements with similar ionic radii. (c) Nonmetallic elements are never found in alloys.

Step-by-Step Solution

Answer

(a) True: Substitutional alloys are generally more ductile than interstitial alloys due to their lattice structure allowing atoms to move easily past each other. (b) False: Interstitial alloys typically form between elements with dissimilar ionic radii, where the solute atoms have smaller radii compared to the solvent atoms. (c) False: Alloys can contain non-metallic elements that enhance their properties, such as carbon in carbon steel or silicon in silicon brass.

Step 1: Statement (a): Substitutional alloys tend to be more ductile than interstitial alloys.

To verify this statement, let's consider the nature of bonding in both types of alloys. Substitutional alloys involve the substitution of one atom for another, maintaining the lattice structure of the base metal. This structure is relatively ductile because the solute atoms can easily move past each other. On the other hand, interstitial alloys have solute atoms occupying interstitial positions, leading to a more complex lattice structure where the solute atoms are surrounded by atoms of the solvent. As a result, interstitial alloys are less ductile than substitutional alloys. Therefore, this statement is true.

Step 2: Statement (b): Interstitial alloys tend to form between elements with similar ionic radii.

Interstitial alloys form when solute atoms are small enough to fit into the interstitial positions in the lattice structure of the solvent. Hence, formation of interstitial alloys occurs between elements with dissimilar ionic radii (not similar), where the solute atoms have smaller radii than the solvent atoms. Therefore, this statement is false.

Step 3: Statement (c): Nonmetallic elements are never found in alloys.

Alloys are mixtures of metals, but they can also contain non-metallic elements that can enhance the properties of the alloy, such as by increasing its hardness or improving its electrical conductivity. Examples of such alloys include carbon steel (iron with carbon) and silicon brass (copper and zinc with silicon). Thus, nonmetallic elements can indeed be found in alloys. Therefore, this statement is false.