Fractional distillation versus simple distillation relies on differences in boiling points. Which statement is true?

• A. It separates liquids with different boiling points
• B. It separates mixtures with identical boiling points
• C. It requires all liquids to be nonvolatile
• D. It does not rely on boiling point

Answer: (A)

Distillation works because different substances vaporize at different temperatures. When you heat a mixture, the component with the lower boiling point forms vapor first and can be collected as a separate liquid after cooling. Fractional distillation uses a column to create many opportunities for vapor to re-condense and re-vaporize, improving separation when the boiling points are close. So the true statement is that distillation separates liquids with different boiling points. The idea that it separates mixtures with identical boiling points isn’t right, since they would vaporize together. It also isn’t about all liquids being nonvolatile, because distillation relies on volatility to produce vapor. And obviously it does rely on boiling points to separate the components.