Question

an aqueous solution contains 2 solutes A&B.A is soluble in hexane,B is not.Hexane is liquid at rom temperature
and does not mix with water.The density
of hexane at room temperature is 0.7g/dm3.Describe giving full practical details how you would produce a pue sample of solute A.

Answer 1

I wonder what the vapor pressure of A and B is in solid form.

If the vapor pressure is low, then one way is to freeze dry the aqueous solution under vacumn, to produce a mass of crystals of A and B. Then, mix that with hexane, to dissolve A, filter to remove B. Then freeze dry under vacumn the solution, and A is left.

Another way to separate <i>some</i> of the A is to pour hexane into the aqueous solution, shake like the dickens, then let the system settle, when separated, draw off the hexane, and evaporate leaving only A crystals.

But being a Rube Goldberg kind of guy, I like freeze drying.

Answer 2

Bob Pursley's Rube Goldberg deal sounds good. I like Rube Goldberg separations, too, however, I think a simple extraction procedure would work just as well. A dissolves in hexane, B is not soluble in hexane. Voila! A dissolves in hexane and two or three separate extractions would get most of A, then evaporate the hexane.