Question

LiCl is soluble in:
A. Pyridine
B. Benzene
C. Both A and B
D. ${H_2}$

Answer 1

Hint: At higher temperature metals of group-1(alkali metals) form ionic compounds like LiCl. Lithium is more polarizing and hence more likely to form covalent compounds than the other metals.

Step by step answer:we must be aware of the fact that solubility in polar solvent decreases while that in relatively non-polar solvent solubility increases. Now let us discuss the solubility of ionic compounds like LiCl.
Solubility depends upon various factors like lattice energy, polarization, entropy etc. since polarization is a dominant factor and we know that it increases with the size of anion and hence the covalent character is maximum in lithium chloride and polarizing power as well because of the larger size of chloride the anion in the ionic compound.
Covalency is favoured due to small size of cation and large size of anion as stated under Fajan’s rules. Therefore lithium chloride will be covalent due to the small size of positive ion that is lithium and large size of negative ion that is chloride. Hence LiCl will be non-polar. We know that like dissolves like therefore the non-polar lithium chloride will be soluble in a nonpolar solvent only. From the given options we can find out that benzene and pyridine are non-polar solvents as benzene is a cyclic chain of hydrocarbons that contains C-C or C-H bonds only hence it is non-polar. Similarly pyridine is non-polar as well.
Hence due to better solute-solvent interaction LiCl will be soluble in both pyridine and benzene.

Therefore the correct option is C.

Note: Pyridine is a heterocyclic compound that has a similar structure to benzene, it just has nitrogen attached in the place of one of the carbons in the chain. Polarizing power depends on the power of the ion to distort the other ion. Hence if the polarization is large electrons are drawn from the negative ion towards the positive ion, resulting in higher concentration of electrons between the two nuclei and a large degree of covalent character results.