Question

Why are lithium salts mostly hydrated?

Answer 1

Hint :A salt or ionic compound in which a number of water molecules are attracted by the ions within its crystalline structure(lattice) is called Hydrated salt. These water molecules may be referred to as water of crystallization or water of hydration. The term “Hydrate” is used to indicate that a substance contains loosely bonded water in inorganic chemistry and organic chemistry.

Complete Step By Step Answer:
Lithium is the smallest in size among the alkali metals. This is the reason why the $ L{i^ + } $ ion has the ability to polarize water molecules more easily when compared to other alkali metals. As a result, water molecules get attached/bonded to lithium salts as water of crystallization.
Hence, lithium salts such as tri-hydrated lithium chloride ( $ LiCl.3{H_2}O $ ) are commonly hydrated. As the size of the ions increases, their polarizing power decreases. Thus, hydration enthalpies decrease. Hence, lithium salts mostly hydrated than other alkali metal ions usually form anhydrous salts.

Note :
The hydration number depends on the concentration of the compound in solution and the identity of the compound. In order to determine the formula of the hydrate (Anhydrous solid. $ x{H_2}O $ ), the number of moles of water per mole of anhydrous solid ( $ x $ ) will be calculated by dividing the number of moles of water by the number of moles of the anhydrous solid. When compounds are dissolved in water, the water molecules form a solvation shell surrounding the solute.