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

Question

Owen Ambrose · Accepted Answer

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

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... #NaCl(s) stackrel(H_2O)rarrunderbrace([Na(OH_2)_6]^+ + [Cl(H_2O)_4]^-)# #" 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 #NaCl(s)#. Alternatively, the solution could be boiled, and the water vapour condensed to give more or less pure water.....

Serenity Allen · Answer

undefined Filtering would not work to separate water from salt in a saltwater mixture because salt dissolves in water, forming a homogeneous solution. Since salt particles are dissolved at the molecular level, they are too small to be filtered out by a typical filter, which can only separate solid particles from liquids in a heterogeneous mixture.