Which of the following is true regarding choosing a solvent for recrystallization?

Choosing an appropriate solvent for recrystallization is crucial for the success of the process, and the requirement that the desired solid must be completely soluble in a hot solvent is foundational to this technique. When a solid is fully dissolved in a hot solvent, it allows for the potential for recrystallization upon cooling. As the solution cools, the solubility of the solid decreases, leading to crystallization as the desired compound comes out of solution.

This complete solubility at elevated temperatures ensures that when the solution is prepared, all of the desired compound can be brought into solution, which maximizes the yield of crystals upon cooling. The effective separation of impurities, which may either remain dissolved in the solvent or not crystallize at lower temperatures, is also facilitated by this requirement.

Understanding this principle is key in recrystallization because it ensures that the purification of the compound is optimized, allowing for maximum recovery of the pure product in crystalline form when the solution is allowed to cool.