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SolutionsDistillation

1. Which distillation?

Give the most suitable type of distillation for:

  1. Recovering diethyl ether (b.p. 35 °C) from a solution of a non-volatile solid.
  2. Separating hexane (b.p. 69 °C) and heptane (b.p. 98 °C).
  3. Purifying a liquid that boils at 280 °C but decomposes above 200 °C.
  4. Obtaining the essential oil of lavender.
  1. Simple distillation: the solid is not volatile.
  2. Fractional distillation: the difference in boiling points (29 °C) is small.
  3. Reduced-pressure (vacuum) distillation.
  4. Steam distillation.

2. Boiling at a lower temperature

Why does a liquid boil at a lower temperature when the pressure is reduced?

A liquid boils when its vapour pressure equals the external pressure. If the external pressure is lower, that value is reached at a lower temperature.

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