The low solubility of LiF and that of CsI in water are respectively due to which of the following properties of the alkalie metal ions ?

Options

A. Higher hydration enthalpy of `Li^(+)`, higher lattice enthalpy of `Cs^(+)`
B. Smaller hydration enthalpy of `Li^(+)`, higher lattice enthalpy of `Cs^(+)`
C. Smaller lattice enthalpy of `Li^(+)`, higher hydration enthalpy of `Cs^(+)`
D. Higher lattice enthalpy of `Li^(+)`, smaller hydration enthalpy of `Cs^(+)`

Answer

D

Explanation

If hydration energy is greater as compare to lattice energy then the salt is soluble, and if hydration energy is lesser as compared of lattice energy, then salt is insoluble.
LiF is almost insoluble due to high lattice energy. Both ions in LiF are very small. In this case, hydration energy is very less.
In case of Csl both ions are larger in size. as a result both the ions in Csl are less hydrated therefore, its hydration energy will decrease. Hence, it insoluble in water.