Question

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

• A. Higher hydration enthalpy of $L{i}^{+}$, higher lattice enthalpy of $C{s}^{+}$
• B. Smaller hydration enthalpy of $L{i}^{+}$, higher lattice enthalpy of $C{s}^{+}$
• C. Smaller lattice enthalpy of $L{i}^{+}$, higher hydration enthalpy of $C{s}^{+}$
• D. Higher lattice enthalpy of $L{i}^{+}$, Smaller hydration enthalpy of $C{s}^{+}$

Answer 1

The correct option is D Higher lattice enthalpy of $L{i}^{+}$, Smaller hydration enthalpy of $C{s}^{+}$

Low solubility of $LiF$ and that of $CsI$ in water is due to the fact that though $L{i}^{+}$ is having high hydration energy but it has higher lattice enthalpy when present in $LiF$, this lattice enthalpy is higher than hydration energy due to which its solubility is less. In case of $CsI$ , though lattice energy is less, but $C{s}^{+}$ is having less hydration enthalpy due to which it is less soluble in water.