Consider the chemical equation.
$N{a}^{+}\left(g\right)+C{l}^{-}\left(g\right)\to N{a}^{+}C{l}^{-}\left(s\right)$

For 1 mole of NaCl(s)
Lattice enthalpy = +788 kJ mol^-1
${\Delta }_{hyd}{H}^0=-784kJmo{l}^{-1}$
 The enthalpy of solution is calculated as