2.7 Distillation, Filtration, Crystallisation

Question 1

Simple distillation

Answer 1

You can use simple distillation to separate a solvent from a solution. It works because the dissolved solute has a much higher boiling point than the solvent.

When it is heated, the vapour evaporates and condenses.

Question 2

Fractional distillation

Answer 2

You can use fractional distillation to separate a pure liquid from a mixture of liquids. It works when the liquids have different boiling points.

It is used to separate ethanol from water.

Question 3

Filtration

Answer 3

If a precipitate has been produced, to separate it, you filter it, leaving behind the precipitate on the filter paper.

Question 4

Crystallisation

Answer 4

If a soluble salt has been produced, to separate it, you would first warm the solution to allow the solvent to evaporate, allow it to cool and then the solid will come out of the solution and crystals will start to grow which can be obtained and patted dry.

Question 4

Paper chromatography

Answer 4

Chromatography is used to separate mixtures. It has a stationary phase and a mobile phase and the separation depends on the distribution of substances.

Rf value = distance moved by substance / distance moved by solvent

Different compounds have different Rf values in different solvents.