Compare evaporation, crystallization and distillation. In which situation, would you prefer each of these over the others?
Evaporation is a process where we allow a solvent to evaporate to get a solute, such as salt from a salt solution. In this process, the solvent disappears, and only the solid solute is obtained.
Crystallization is a technique used to get a pure solid from its saturated solution. It is useful for obtaining pure solid crystals, such as obtaining panga salt from concentrated sea brines.
Distillation is a process used to separate a homogeneous mixture of two miscible liquids or a liquid from a solution containing dissolved solids. It allows the recovery of the solvent and requires the liquids to differ in boiling point by at least about 25 °C.
We prefer evaporation over others when we only need to obtain the solute and the loss of the solvent is acceptable, such as producing karkatch salt from seawater. We prefer crystallization over evaporation when we need to obtain a highly pure solid from its saturated solution.
We prefer distillation over evaporation when we need to recover the solvent along with the solute, or when separating two miscible liquids with a sufficient difference in boiling points, like separating a mixture of acetone and water.
Explanation
The answer compares the three separation techniques using the provided context. Evaporation results in the loss of the solvent to obtain the solute. Crystallization yields a pure solid from a saturated solution. Distillation is used to separate miscible liquids (with at least a 25 °C boiling point difference) or to recover the solvent from a solution. The preference situations are derived directly from the text: evaporation is preferred when solvent loss is acceptable (e.g., karkatch salt), crystallization for pure solids, and distillation for solvent recovery or separating miscible liquids like acetone and water.
Solution Steps
Step 1: Define and compare Evaporation (solvent evaporates and disappears, leaving the solute).
Step 2: Define and compare Crystallization (obtains a pure solid from a saturated solution).
Step 3: Define and compare Distillation (separates miscible liquids with >25 °C boiling point difference, recovers solvent).
Step 4: State preference for Evaporation (when only the solute is needed and solvent can be lost).
Step 5: State preference for Crystallization (when a highly pure solid is needed from a saturated solution).
Step 6: State preference for Distillation (when solvent recovery is needed or separating miscible liquids like acetone and water).