# Question #4d493

Feb 10, 2015

The salt precipitates because sodium chloride is much less soluble in ethanol than it is in water. This happens because of the structure of ethanol, or $C {H}_{3} C {H}_{2} O H$.

The $\text{-OH}$ functional group enables ethanol to hydrogen bond and interact with water molecules. However, the non-polar part of the molecule, which is represented by an ethyl group, $C {H}_{3} C {H}_{2} -$, will prevent ethanol from being able to keep the $N {a}^{+}$ and $C {l}^{-}$ ions separated from each other in solution.

As a result, ethanol will react more with the water molecules than with the ions. This implies that fewer water molecules will be available to keep the aforementioned ions apart in solution $\to$ salt precipitates.

Less available water molecules to interact with the ions is equivalent to having an increase in the concentration of the ions in solution.

$\text{Less SOLVENT" => "INCREASED concentration of ions}$

If the solution is saturated, this will automatically result in the precipitation of the salt.