Question

Explain why complete solid solubility may occur for substitutional solid solutions but not for interstitial solid solutions.

Answer 1

Substitutional solid solutions allow for complete solid solubility, while interstitial solid solutions do not.

Step-by-step explanation:

Substitutional solid solutions occur when atoms of one element are replaced by atoms of another element in a crystal lattice. In this type of solid solution, the atoms are similar in size and have similar chemical properties, allowing them to substitute for each other without disrupting the crystal structure. Therefore, complete solid solubility can occur.

On the other hand, interstitial solid solutions occur when smaller atoms or ions occupy the spaces between the larger atoms in a crystal lattice. It is difficult for the larger atoms to be replaced by smaller atoms without disrupting the crystal structure. As a result, complete solid solubility does not typically occur in interstitial solid solutions.

Answer 2

Substitutional solid solutions can achieve complete solid solubility because the solute and solvent atoms can replace each other in the lattice when they are of similar size and compatible chemical properties. Interstitial solid solutions are limited in solubility due to the size of the solute atoms and a limited number of interstitial spaces, along with possible electronic and charge incompatibilities.

Step-by-step explanation:

Complete solid solubility may occur in substitutional solid solutions because the atoms in the solute and the solvent are similar in size and can easily replace each other in the lattice structure. However, interstitial solid solutions have a different scenario; solute atoms are much smaller than solvent atoms and fit into the interstices (spaces) of the solvent lattice. The size and number of these interstices are limited, thus restricting the amount of solute that can be accommodated without distorting the lattice and leading to solubility limits.

Factors like the size of the interstitial spaces, electric charge differences, and the electron configurations of the elements involved can affect the solubility of interstitial solutes. These factors can lead to incomplete solubility as the solute elements may not fit perfectly into the lattice, or differences in electronic nature between the solute and solvent atoms may result in electrical repulsion or an absence of bonding, thus preventing a complete mixture.

In contrast, for substitutional solid solutions, if the solute and solvent atoms are of similar size, and their chemical and electronic properties are compatible, they can replace each other in the crystal lattice, which may result in complete solid solubility throughout the composition range.