12.2 Distillation

Question 1

distillation

Answer 1

separates components from a liquid mixture by taking advantage of their differing boiling points to separate them by evaporation and condensation

the liquid with the lower BP will vaporize first, and the vapour will rise up the distillation column to condense in a water-cooled condenser

the condensate then drips down into a collection flask to form the distillate

Question 2

what is the end product of distillation called?

Answer 2

the distillate

Question 3

requirements for simple distillation

Answer 3

components must have BP that differ by at least 25C

BP should be below 150C

Question 4

apparatus for simple distillation

Answer 4

distilling flask containing the liquid mixture

distillation column containing a thermometer and condenser

receiving flask to collect distillate

(minus vacuum adaptor)

Question 5

superheating

Answer 5

when a liquid is heating to a temperature above its boiling point without evaporation

Question 6

when/why does superheating occur?

Answer 6

occurs when gas bubbles in a liquid are unable to overcome the combination of atmospheric pressure and surface tension

Question 7

methods to prevent superheating?

Answer 7

addition of boiling chips or magnetic stirrers

Question 8

when is vacuum distillation used

Answer 8

used to distill a liquid with a BP above 150C

the vacuum lowers the ambient pressure, decreasing the temperature the liquid must reach to boil

allows use to distill compounds with high BPs at lower temperatures

Question 9

when is fractional distillation used?

Answer 9

to separate 2 liquids with similar BPs (less than 25C apart)

Question 10

fractional distillation method

Answer 10

a fractionation column connects the distillation flask to the condenser

as the vapour pressure rises up the column, the temperature drops slightly and the vapour condenses and drips down the column until it evaporates again

each time the condensate re-evaporates, the vapour consists of a higher proportion of the compound with lower BP

only the vapour with the lowest BP reaches the top of the fractionation column

Question 11

fractionation column

Answer 11

a tall column in which connects the distilling flask and the conenser

the surface area is often increased by the inclusion of inert objects like glass beads or steel wool