Skip to main content
Pearson+ LogoPearson+ Logo
Ch.12 - Solids and Modern Materials
All textbooksBrown 14th EditionCh.12 - Solids and Modern MaterialsProblem 42a,c
Chapter 12, Problem 42a,c

Determine if each statement is true or false: (a) Substitutional alloys are solid solutions, but interstitial alloys are heterogenous alloys. (c) The atomic radii of the atoms in a substitutional alloy are similar to each other, but in an interstitial alloy, the interstitial atoms are a lot smaller than the host lattice atoms.

Verified step by step guidance
1
Understand the concept of substitutional alloys: These are solid solutions where atoms of the solute metal replace atoms of the host metal in the lattice. The atomic radii of the solute and host metals are similar, allowing for substitution without significant distortion of the lattice.
Understand the concept of interstitial alloys: These involve smaller atoms fitting into the interstices (spaces) between the larger host metal atoms in the lattice. The interstitial atoms are significantly smaller than the host atoms, which allows them to fit into the gaps without replacing the host atoms.
Evaluate statement (a): Substitutional alloys are indeed solid solutions because the solute atoms replace host atoms in the lattice, maintaining a uniform structure. Interstitial alloys are not heterogenous; they are also considered solid solutions because the smaller atoms are uniformly distributed within the lattice.
Evaluate statement (c): In substitutional alloys, the atomic radii of the atoms involved are similar, which is necessary for substitution to occur. In interstitial alloys, the interstitial atoms are much smaller than the host lattice atoms, which is why they can fit into the spaces between the host atoms.
Conclude the evaluation: Based on the explanations, statement (a) is false because both substitutional and interstitial alloys are solid solutions. Statement (c) is true because it accurately describes the size relationship between atoms in substitutional and interstitial alloys.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Substitutional and Interstitial Alloys

Substitutional alloys are formed when atoms of a solute replace or substitute for atoms of a solvent in a metal lattice, resulting in a solid solution. In contrast, interstitial alloys occur when smaller atoms fit into the spaces (interstices) between the larger host atoms. Understanding these definitions is crucial for evaluating the statements regarding the nature of these alloys.
Recommended video:
Guided course
01:08
Alcohol Reactions: Substitution Reactions

Atomic Radii and Alloy Formation

The atomic radius refers to the size of an atom, which influences how atoms can pack together in a solid. In substitutional alloys, the atomic radii of the solute and solvent atoms are typically similar, allowing for a uniform structure. Conversely, in interstitial alloys, the interstitial atoms are significantly smaller, which allows them to occupy the spaces between the larger host atoms without disrupting the overall lattice structure.
Recommended video:
Guided course
02:34
Enthalpy of Formation

Homogeneity vs. Heterogeneity in Alloys

Homogeneous alloys, like substitutional alloys, exhibit a uniform composition and properties throughout the material, while heterogeneous alloys have distinct phases or regions with different compositions. This distinction is important for understanding the physical properties and behaviors of different types of alloys, as it affects their mechanical and thermal characteristics.
Recommended video:
Guided course
03:05
Ksp vs Q in Precipitation
Related Practice
Textbook Question

An element crystallizes in a face-centered cubic lattice. The edge of the unit cell is 4.078 Å, and the density of the crystal is 19.30 g>cm3. Calculate the atomic weight of the element and identify the element.

Textbook Question

Which of these statements about alloys and intermetallic compounds is false? (a) Bronze is an example of an alloy. (b) 'Alloy' is just another word for 'a chemical compound of fixed composition that is made of two or more metals.' (c) Intermetallics are compounds of two or more metals that have a definite composition and are not considered alloys. (d) If you mix two metals together and, at the atomic level, they separate into two or more different compositional phases, you have created a heterogeneous alloy. (e) Alloys can be formed even if the atoms that comprise them are rather different in size.

Textbook Question

Determine if each statement is true or false: (b) Substitutional alloys have 'solute' atoms that replace 'solvent' atoms in a lattice, but interstitial alloys have 'solute' atoms that are in between the 'solvent' atoms in a lattice.

Textbook Question

For each of the following alloy compositions, indicate whether you would expect it to be a substitutional alloy, an interstitial alloy, or an intermetallic compound: (a) Fe0.97Si0.03 (b) Fe0.60Ni0.40 (c) SmCo5.