Why CsCl has got more solubility than NaCl though hydration enthalpy of Na is more??????

The solubility of the chlorides decreases as the group descends as the exothermic hydration enthalpy of the ions decreases at a greater rate than the endothermic lattice enthalpy of the ionic compound. This is because the Cl- ion is larger than a molecule of H20 meaning that the decrease in lattice enthalpy (due to the increase in atomic radius of the positive ion as you go down the group) is more significant than the decrease in hydration enthalpy of the cation (the hydration enthalpy of Cl- remains constant). Therefore the overall process becomes more endothermicand solubility decreases down the group as the reaction is less energetically favourable and less likely to go to completion (the ionic solid will exist in dynamic equilibrium with its ions in solution).

Therefore, CsCl is the least soluble of these group 1 chlorides, and NaCl is the most soluble.