Chemistry sample related question?

Question

you are given a sample of crude benzoic acid in which charcoal and salt are the main impurities. Explain how re-crystallisation from water would allow you to remove each impurity and to isolate the benzoic acid.

Answer 1

Dissolve, say, 1 g of sample in 100 mL of water. Heat to near boiling (where NaCl and benzoic acid are soluble). Filter off the charcoal and cool the filtrate in an ice bath (most of the benzoic acid will come out of solution while NaCl will not). Filter off the benzoic acid while cold and wash with cold water.

Answer 2

Carbon not soluble in water.  Dissolve and filter out the charcoal (if it is activated, it can help decolorize the product).  As the solution cools, salt (NaCl I presume) is quite soluble in water and the benzoic acid crystallizes as a pure material.