Final answer:
A good solvent for recrystallization should have low solubility at low temperatures and high solubility at high temperatures. This facilitates the separation of compounds during fractional crystallization.
Step-by-step explanation:
A good solvent for recrystallization should have low solubility at low temperatures and high solubility at high temperatures. This allows the solute to dissolve at high temperatures, making it easier to remove impurities, and then recrystallize out of solution at low temperatures. For example, in fractional crystallization of a mixture of sodium acetate and KBr, water is used as a solvent. At 80°C, both compounds dissolve in water, but at 0°C, only sodium acetate crystallizes out due to its lower solubility. This allows for the separation of the two compounds.