Question

Given a mixture of barium chloride, and potassium chloride, how would we separate one salt from the other?

Answer 1

By exploiting the relative insolubility of barium sulfate.

Explanation:

`BaSO_4` is relatively insoluble in water; `K_(sp)=1.08xx10^(-10)`.

So we mix stoichiometric barium chloride and potassium sulfate:

`BaCl_2(aq) + K_2SO_4(aq) rarr BaSO_4(s)darr + 2KCl(aq)`

The supernatant solution should be `KCl(aq)`. Now this is filtered (or decanted) off to give a solution that should be reasonably pure `KCl(aq)`.

How to get the `KCl(aq)` out of solution? Well you could suck it dry, but this would take forever. A better way would be to add ethyl alcohol to the solution. This solvent would precipitate out the `KCl`. This is collected on a frit, and subjected to extensive drying at elevated temperature.