# What do water molecules disassociate in salt crystals when they are dissolved in water?

Mar 4, 2017

When $\text{sodium chloride, halite,}$ is dissolved in water, the water solvent breaks up the solid ionic structure to give so-called $\text{solvated}$ or $\text{aquated}$ sodium and chloride ions:
$N a C l \left(s\right) \text{+ excess } {H}_{2} O \left(l\right) \rightarrow N {a}^{+} \left(a q\right) + C {l}^{-} \left(a q\right)$
The $N {a}^{+} \left(a q\right)$ species is arguably ${\left[N a {\left(O {H}_{2}\right)}_{6}\right]}^{+}$, a coordination complex if you like, in which the water molecules bind to the metal centre in an ion-dipole interaction. And likewise, chloride ion is solvated. For these reasons, i.e. ionic bonds are broken, and ion-dipoles, are formed, we could classify this dissolution as an example of chemical change.