Question

Why does NaCl dissolve in water?

Answer 1

Because the lattice enthalpy of sodium chloride is almost precisely balanced by the hydration energy.

Explanation:

We represent the dissolution of sodium chloride in water in this way:

`NaCl(s) rarr Na^(+)(aq) + Cl^(-)(aq)`

`(aq)` stands for the aquated ion, because each ion is solvated by, or aquated by, up to 6 water molecules. The lattice energy of sodium chloride (which is the energy released when the lattic forms) is almost precisely balanced by the hydration energy, when the water solvent molecules hydrate the `Na^+` and `Cl^-` ion. This equivalence is why the dissolution is thermodynamically feasible.