Explain the principle of simple distillation and when it is effective.

• A. Simple distillation separates liquids with large difference in boiling points (>70°C) by vaporizing the more volatile component and condensing it elsewhere.
• B. Simple distillation separates mixtures based on differences in density only.
• C. Simple distillation requires a fractionating column for separation.
• D. Simple distillation can separate azeotropic mixtures.

Answer: (A)

Simple distillation uses differences in boiling points to separate components. When you heat the mixture, the component with the lower boiling point tends to vaporize first. That vapor travels to a condenser, where it cools and returns to the liquid phase in a separate receiving vessel. The less volatile component remains behind, so you can collect mostly one component in the distillate.

This method works best when the two liquids have a large difference in boiling points—so the vapor is enriched in the more volatile component and little of the higher-boiling component co-distills. A typical practical guideline is a substantial difference, often around 70°C or more, to achieve clean separation without a fractionating column.

The other statements don’t fit the concept. Separation by simple distillation is not based on density differences, and a fractionating column is not required for simple distillation (that’s for fractional distillation when boiling points are closer). Simple distillation also cannot reliably separate azeotropic mixtures, which boil without changing composition and require special techniques.