The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to -
1. Ionic nature of lithium fluoride
2. High lattice enthalpy
3. High hydration enthalpy for lithium ion
4. Low ionisation enthalpy of lithium ion
Hint: If lattice enthalpy is greater than hydration enthalpy then solubility increases.