Why sodium hydroxide is much more water soluble than chloride?

Explanation

Na OH is much more soluble than NaCl.
Enthalpy of a solution can be expressed as the sum of lattice enthalpy and enthalpy of hydration of a compound.
`Delta H` solu NaCl = + 3 . 9 KJ/mol
`Delta H ` solu NaOH = - 44 . 5 KJ/mol
` DeltaH_(0)` Lattice enthalpy of NaCl = + 787. 6 KJ
Hydration enthalpy = - 784 . 1 KJ
Therefore `Delta H` solu = + 787 . 6 - 784 . 1
= - 3 . 5 KJ
Dissolution of NaCl is accompanied by very small heat change so solubility of NaCl is less than NaOH .