Question

Suppose you have an impure solid that needs to be purified. The solid is insoluble in cold water and slightly soluble in hot water; it’s soluble in both cold and hot ethanol; it’s insoluble in cold toluene and soluble in hot toluene; and it’s slightly soluble in cold acetic acid and soluble in hot acetic acid. Which solvent would be the most suitable for recrystallizing the impure solid? Explain your reasoning.

Answer 1

Toluene will be the most suitable solvent.

Step-by-step explanation:

Recrystallization is the process where an impure solid is dissolved in a solvent at a high temperature (to accelerate the process). Then, the mixture is cooled down, so the solid must be formed again, this time without the impurities, which are dissolved in the solvent.

So, a good solvent, must dissolve all the solute in high temperatures, and can't dissolve it in low temperatures. The only one which does that is the toluene.