Answer
$43.4\,JK^{-1}mol^{-1}$
Work Step by Step
$\Delta S^{\circ}_{rxn}=\Sigma n_{p}S^{\circ}(products)-\Sigma n_{r}S^{\circ}(reactants)$
$=[S^{\circ}(NaCl,aq)]-[S^{\circ}(NaCl,s)]$
$=(115.5\,JK^{-1}mol^{-1})-(72.13\,JK^{-1}mol^{-1})$
$=43.4\,JK^{-1}mol^{-1}$
$\Delta S^{\circ}_{rxn}$ is positive because of the increase in entropy.
