Question

The aqueous solutions of lithium salts are poor conductors of electricity as compared to that of other alkali metals because of:
A) High ionization energy
B) High electronegativity
C) Lower ability of \[{\text{L}}{{\text{i}}^{\text{ + }}}\] ions to polarize water molecules
D) Higher degree of hydration of \[{\text{L}}{{\text{i}}^{\text{ + }}}\] ions

Answer 1

Hint: The material which allows electricity through them is known as the conductors and this property of the substances or material is known as conductivity. The type of material, its surface area, temperature affect the conductivity of the material. In the case of the solution, as the numbers of ions increase the conductivity of the solution also increases, that is a concentration of the solution affects the conductivity.

Complete step-by-step answer:
The aqueous solution of any salt is obtained by dissolving the salt in the water. The number of ions in the solution responsible for its conductivity. As the number of ions increases the conductivity of the solution also increases.In the case of the hydration process, ions of the salt are surrounded by the water molecules by the electrostatic force of attraction.

Li, Na, K, Rb, and Cs are the alkali metals and in salts, they carry a +1 charge on them.
In the group from top to bottom ionic size increases therefore the order of the size of alkali cation is as follows:
\[{\text{L}}{{\text{i}}^{\text{ + }}}{\text{ < }}\,{\text{N}}{{\text{a}}^{\text{ + }}}{\text{ < }}\,{{\text{K}}^{\text{ + }}}{\text{ < }}\,{\text{R}}{{\text{b}}^{\text{ + }}}{\text{ < }}\,{\text{C}}{{\text{s}}^{\text{ + }}}\]

As the size of the ion decreases, the degree of hydration increases because of a stronger force of attraction between the ion and water molecules.The high degree of hydration indicates more large numbers of the water molecules surround the ions that lead to a decrease in the mobility of the ion and hence, decreases the conductivity of the ion.

Here Lithium-ion has the lowest size and possesses the highest degree of hydration indicates a large number of the ions surrounding the lithium-ion and hence, it possesses the least mobility. Here. Option (A) given is high ionization energy is incorrect. Now, option (B) high electronegativity is also incorrect.

Here, option (C) is given as a lower ability of the lithium ions to polarise the water molecule. It is also incorrect because as the size of the lithium-ion is lowest it can polarize water molecules more compared to other alkali metal ions.

Now, option (D) given is the higher degree of the hydration of \[{\text{L}}{{\text{i}}^{\text{ + }}}\] ions is the correct answer to the given question.

Note:In the case of the aqueous solution, hydration affects the conductivity of the solution. The higher the degree of the hydration, the more numbers of the water molecules surround the ion and therefore, decrease the mobility of the ion. The size of the ion is inversely proportional to the degree of hydration.