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Question Video: Identifying a Piece of Glassware Used in Fractional Distillation Chemistry

The image shows a piece of labware often used in fractional distillation. What name is given to this piece of labware?


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.

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