Which of the following separation techniques can be employed in obtaining solvent from its solution?

Analysis

The question asks for a technique used to recover a solvent (the liquid part of a solution) from a solution. In a solution, the solute is dissolved in the solvent, and we need to separate them such that the solvent is collected rather than lost to the atmosphere.

Concept Explanation

To choose the right technique, we must understand what happens in each process:

• Evaporation: This involves heating a solution until the solvent turns into vapor and escapes into the atmosphere. While this leaves the solute behind, the solvent is lost.
• Distillation: This is a process of heating a liquid to form vapor and then cooling the vapor back into a liquid (condensation). This allows you to collect the pure solvent in a separate container (the distillate).
• Filtration: This is used to separate an insoluble solid from a liquid. It cannot separate a dissolved solute from a solvent.
• Precipitation: This is a chemical process where a dissolved substance is converted into an insoluble solid (precipitate). It is not a standard physical separation technique for recovering a solvent.

Step-by-Step Solution

1. Identify the goal: We need to recover the solvent.
2. Evaluate the options: • Evaporation loses the solvent to the air. • Filtration only works for mixtures, not solutions. • Precipitation changes the chemical state of the solute.
3. Analyze Distillation: In simple distillation, the solution is boiled. The solvent (which has a lower boiling point than the solute) vaporizes. The vapor travels through a condenser, where it is cooled and turns back into a liquid. This liquid is then collected. This is the standard laboratory method for obtaining a pure solvent from a solution.

Conclusion

Distillation is the only technique listed that allows for the recovery of the solvent in liquid form.

Exam Tip: Always remember the difference between Evaporation and Distillation: If the question asks to recover the solute (like salt from saltwater), use evaporation. If the question asks to recover the solvent (like pure water from saltwater), use distillation.