Question

Sodium chloride is soluble in water but not in benzene because

• A. $\Delta {\text{H}}_{\text{Solvation}}<\Delta {\text{H}}_{\text{Lattice energy}}$ in water and
  $\Delta {\text{H}}_{\text{Solvation}}>\Delta {\text{H}}_{\text{Lattice energy }}$ in benzene
• B. $\Delta {\text{H}}_{\text{Solvation}}>\Delta {\text{H}}_{\text{Lattice energy }}$ in water and
  $\Delta {\text{H}}_{\text{Solvation}}<\Delta {\text{H}}_{\text{Lattice energy}}$ in benzene
• C. $\Delta {\text{H}}_{\text{Solvation}}=\Delta {\text{H}}_{\text{Lattice energy }}$ in water and
  $\Delta {\text{H}}_{\text{Solvation}}<\Delta {\text{H}}_{\text{Lattice energy}}$ in benzene
• D. $\Delta {\text{H}}_{\text{Solvation}}<\Delta {\text{H}}_{\text{Lattice energy }}$ in water and
  $\Delta {\text{H}}_{\text{Solvation}}=\Delta {\text{H}}_{\text{Lattice energy }}$ in benzene

Answer 1

Answer: (B)

Hydration energy is released during dissolution in the water while lattice energy is required to the energy to break the crystal. So, Lattice energy is endothermic and hydration nergy is exothermic.
For a compound to be soluble, the solvation or hydration energy must be greater than the lattice energy. Since, NaCl is soluble in water but insoluble in benzene.
$\Delta {\text{H}}_{\text{Solvation}}>\Delta {\text{H}}_{\text{Lattice energy }}$ in water
and
$\Delta {\text{H}}_{\text{Solvation}}<\Delta {\text{H}}_{\text{Lattice energy}}$ in benzene