The crystallization step in recrystallization removes which category of impurities?

The crystallization step in recrystallization effectively removes impurities that are incorporated within the crystal lattice of the solid. During the recrystallization process, a solute is dissolved at high temperatures, allowing for the formation of a saturated solution. As the solution cools, the solute begins to crystallize, forming a pure solid structure.

Impurities that are structurally similar to the solute or are present in low concentrations often get trapped in the growing crystal lattice. However, due to differences in solubility, these impurities can either remain in the solution or are not structurally integrated into the new crystal form, making them removable through this technique.

Overall, the effectiveness of recrystallization hinges on the selective crystallization of the solute, which allows for the exclusion of these lattice-bound impurities, resulting in a purer product.