What must a solvent do to be effective for recrystallization?

For a solvent to be effective in recrystallization, it must effectively dissolve the solute when heated, allowing for a concentrated solution, and then allow crystals to form upon cooling. This thermal solubility behavior is crucial because recrystallization relies on the differences in solubility at varying temperatures.

When the solvent is hot, it should dissolve the solute well, leading to a saturated solution. On cooling, the solute's solubility decreases, promoting the formation of crystals as the solute is less soluble at the lower temperature. The ideal outcome is to have the desired compound crystallize out of solution while impurities remain dissolved.

The characteristics of the solvent directly influence the efficiency and success of the recrystallization process. For instance, a solvent that dissolves the solute well at high temperatures but poorly at low temperatures can effectively separate the desired crystals from impurities.

Other options do not align with the requirements for effective recrystallization. A solvent that dissolves the solute when cold and allows for crystallization when heated contradicts the principle of exploiting differences in solubility with temperature changes. A solvent being volatile or mixing uniformly regardless of temperature does not provide the necessary conditions for successful crystallization. Thus, the solvent's behavior