Question

The solubility order of the chlorides of the alkali metals is:

A. NaCl > KCl > RbCl > CsCl

B. CsCl > RbCl > KCl > NaCl

C. KCl > NaCl > RbCl > CsCl

D. CsCl > RbCl > NaCl > KCl

Answer 1

Hint: Alkali metals are the group 1 elements in the periodic table. In this question characterize the different properties represented by alkali metals like stability, ionization enthalpy, or lattice enthalpy, atomic size, and solubility.

Complete step by step answer:

- First, we know that Li to Cs i.e. Li, Na, K, Rb, and Cs are group 1 alkali metals, and their atomic size increases as we move down the group.

- Now if we relate the atomic size with the other properties, then size of cation increases moving down the group due to the presence of less attraction between cation and anions.

- The decrease in attractive force leads to the decrease in stability.

- Thus, the lattice enthalpy of ionic solid i.e. alkali metal chloride decreases down the group.

- Now, if we combine all these factors, then the solubility of the chlorides of the alkali metal decreases down the group.

Therefore, the order is NaCl > KCl > RbCl > CsCl. So, the correct option is A.

Note: Remember the group 1 elements and the property represented by the elements in the periodic table. Don’t get confused in between the order of the properties down the group whether it increases or decreases.