Question

Why LiI is more soluble than KI in ethanol?

Answer 1

Hint: take a look at the structures of both the compounds and the size of each ion. The one which has a lower size will be soluble more easily. Also solubility is something to do with the polarizing capabilities of the compound.

Complete Step By Step Answer:
LiI is lithium, Iodide is a component of lithium iodine and KI is potassium iodide, a component of potassium and iodine.
In the question it is given that LiI is more soluble than KI in ethanol now why does this happen. When we take a look at the structure of LiI, the lithium ion is smaller in size because of this its polarizing capability is very high. This higher polarizing power enables LiI to polarize the electron cloud around an iodide ion thus resulting in a greater covalent character in LiI. Therefore LiI is more easily soluble in ethanol. On the other hand, KI is predominantly an ionic compound, thus it is insoluble in ethanol.
Polarization is a property of an ionic bond. Polarization of an ionic bond results in an ionic bond with covalent character. When the polarization of any compound increases, the intermolecular forces between them also increases and this increase in the intermolecular forces results in increasing the solubility of the compound.

Note:
Solubility also depends upon the ionic trend; the more ionic the compound is, the more it is soluble. The ionic trends are determined by the fajans rules. Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. This slight separation of charge makes one side of the atom somewhat positive and the opposite side somewhat negative.