Video Transcript
A solid alloy is produced by combining small amounts of element B with a metal A. Why might this alloy be described as a solid solution? (A) Atoms of B disrupt the lattice of A to produce a highly disordered structure
resembling a solution. (B) Atoms of B can move freely through the lattice of A, like solutes in a
solvent. (C) Atoms of B randomly replace atoms in the lattice of A, like solutes in a
solvent. (D) Atoms of B increase the electrical conductivity of A, like solutes in a
solvent. Or (E) atoms of B disrupt the lattice of A to produce voids that can be occupied by
solvents.
Let’s start by clearing some space.
A metallic alloy is a mixture that contains at least two different types of
elements. To be considered an alloy, the mixture must always contain at least one metal
element. We say that an alloy, especially one containing two elements in unequal proportions,
contains a major and minor component. This definition is similar to a solution, which is also a mixture that contains at
least two different chemical elements. In a solution, a solute dissolves in a solvent. The solvent is the major component, and the solute is the minor component. Because of these similarities, alloys are sometimes described as being metallic solid
solutions.
Alloy atoms are also arranged similarly to atoms in a liquid solution, meaning that
the atoms of at least one minor chemical element are dispersed or dissolved
throughout the lattice of another major metal element.
Alloys are typically formed by heating up metal elements. They are heated until they are in a liquid state. The elements are then mixed together. Once allowed to solidify, the atoms become fixed in an ordered space. And the resulting alloy has different properties than the individual components.
We are asked why a solid alloy that is produced by combining small amounts of element
B with a larger amount of metal A might be described as a solid solution. Let’s look through the answer choices in turn.
Option (A) states that atoms of B disrupt the lattice of A to produce a highly
disordered structure resembling a solution. Though a lattice can be disrupted, it is not considered highly disordered since a
lattice, even a disrupted one, has order by definition. Thus, option (A) is not the answer to this question.
Option (B) states that atoms of B can move freely through the lattice of A, like
solutes in a solvent. As atoms of element B are not fixed in space, this is closer to the description of a
liquid solution. For this reason, answer choice (B) is incorrect.
Option (C) states that atoms of B randomly replace atoms in the lattice of A, like
solutes in a solvent. This closely matches the description of something called a substitutional alloy,
where atoms of one element can substitute the atoms of another element if they have
similar bonding characteristics and atomic diameters. So it seems like this description does match with that of an alloy. So option (C) is likely to be the answer to this question. But to confirm, let’s look at options (D) and (E).
Option (D) states that atoms of B increase the electrical conductivity of A, like
solutes in a solvent. While an alloy can have increased electrical conductivity compared to its parent
elements, a solution, by definition, does not increase electrical conductivity. Therefore, answer choice (D) is incorrect.
Option (E) states that atoms of B disrupt the lattice of A to produce voids that can
be occupied by solvents. An alloy can disrupt the lattice of a metal and produce voids. However, the production of voids has no bearing on the definition of a solid
solution. Thus, option (E) is incorrect.
We can now bring back all the answer choices. We now know that the alloy given in the question can be described as a solid solution
as atoms of B randomly replace atoms in the lattice of A, like solutes in a
solvent. This is answer choice (C).
