Chemistry 30 Diploma Practice Exam

Fractional distillation relies on differences in boiling points and uses a fractionating column to create many theoretical plates, allowing repeated vaporization and condensation that separate components with close boiling points into distinct fractions. When the mixture is heated, the component with the lower boiling point tends to go into the vapor phase first. The vapor rises through the column, condensing on cooler surfaces and re-vaporizing, so the vapor reaching the condenser is progressively enriched in the more volatile component. By collecting portions of distillate at different temperatures, you separate the mixture into fractions corresponding to different boiling ranges. This is different from simple distillation, which lacks the column and therefore provides poorer separation unless the boiling points are very far apart, and from vacuum distillation, which is about lowering pressure to distill heat-sensitive materials rather than enhancing separation by multiple theoretical plates.