JEE Main202226 Jul 2022Evening ShiftChemistrys Block ElementsActual
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R . Assertion A : LiF is sparingly soluble in water. Reason R : The ionic radius of Li + ion is smallest among its group members, hence has least hydration enthalpy. In the light of the above statements, choose the most appropriate answer from the options given below.
Options
- ABoth A and R are true and R is the correct explanation of A
- BBoth A and R are true but R is NOT the correct explanation of A
- CA is true but R is false
- DA is false but R is true
Correct answer
C. A is true but R is false
Step-by-step solution
The low solubility of LiF in water is due to its high lattice enthalpy. The hydration enthalpies of alkali metal ions in aqueous solution decreases with increase in ionic sizes. Li + > Na + > K + > Rb + > Cs + Li + has maximum degree of hydration and for this reason lithium salts are mostly hydrated, e.g., LiCl . 2 H 2 O Hence, A is true and R is false.