You need to separate water from salt in a saltwater mixture. Why would it not work to filter the mixture?

Jul 26, 2018

Because the salt and the water form an homogeneous solution...

Explanation:

The act of dissolution in this scenario is to all intents and purposes a chemical reaction... Bonds and broken, and new substances are formed. We start with solid salt...we end with a solution of aquated ions...

$N a C l \left(s\right) \stackrel{{H}_{2} O}{\rightarrow} \underbrace{{\left[N a {\left(O {H}_{2}\right)}_{6}\right]}^{+} + {\left[C l {\left({H}_{2} O\right)}_{4}\right]}^{-}}$
$\text{ AQUATED IONS, i.e. NaCl(aq)}$

The sodium ions, and chloride ions, coordination complexes if you like, remain in solution. There is no solid to separate by filtration. Ethanol could be added to the solution, and this would precipitate much of the solute as $N a C l \left(s\right)$.

Alternatively, the solution could be boiled, and the water vapour condensed to give more or less pure water.....