Video Transcript
The image below shows a piece of
labware often used in fractional distillation. What name is given to this piece of
labware?
The question asks about
distillation. Distillation is a method for
separating mixtures where the mixture is heated until the more volatile components
turn into gases, which are then condensed and collected in a separate vessel. There are two types of
distillation: simple distillation and fractional distillation.
Simple distillation is usually used
to separate a mixture of two liquids whose boiling points differ by more than 50
degrees Celsius, although simple distillation can also be used to purify a liquid
which is contaminated with a soluble solid solute. Fractional distillation is usually
used to separate mixtures of more than two components, where the difference in
boiling point between two substances is about 25 degrees Celsius or less.
We are specifically asked about
fractional distillation. Let’s define fractional
distillation. Fractional distillation is a type
of distillation where the components of a mixture are separated in sequence by first
heating the mixture, then passing the vapors through a fractionating column that
improves their purity, then condensing the purified vapors into liquid, and finally
collecting the liquefied vapors. Both simple and fractional
distillation have a similar setup, although simple distillation does not have step
two, the fractionating column.
The diagram shows the experimental
setup for fractional distillation. The mixture to be separated sits in
a distillation flask. It is heated, and sometimes boiling
chips are placed into the liquid mixture to give a more controlled boil and prevent
bumping. This is step one.
Volatile vapors enter the
fractionating column. In the fractionating column, a
series of cycles of condensation and reevaporation occurs. And the vapors are separated into
their different components and are, thus, purified as they move up the column. This is step two.
Vapors move into the adapter past a
thermometer, which allows us to monitor the boiling point of the purified substance
in the vapor phase and, thereby, identify what substance is coming off at that point
in time. The vapors then move down into a
piece of apparatus called the condenser. Do you notice this is the piece of
labware that we were asked about?
The condenser consists of an outer
glass tube, or jacket, and an inner tube. Water, the coolant, flows into the
bottom of the jacket and out the top. This constant movement of water
cools down the vapors in the inner tube of the condenser, and purified vapors are
condensed from gas to liquid. This is step three.
Finally, this purified liquid moves
through an adapter into a collection flask. And this is step four. Because cool water is allowed to
enter the bottom of the condenser, the temperature at the bottom of the condenser is
much cooler than at the top. The water leaving the condenser is
slightly warmer, and this configuration is optimal to condense gas to liquid in the
inner tube.
Finally, what name is given to the
piece of labware shown in the diagram? The answer is condenser.
