Video Transcript
The experimental setup for a
fractional distillation experiment is shown in the diagram below. What is the name of the piece of
apparatus labeled A? (A) Evaporation column, (B) vapor
column, (C) fractionating column, (D) boiling column, (E) volatility column.
Fractional distillation is a
technique typically used on mixtures that can be separated into two or more
fractions and in which the difference between the boiling points of each component
is less than 25 degrees Celsius. Let’s clear some space to go
through the sequence of steps used in fractional distillation.
First, the mixture is heated in a
round-bottom flask by using a Bunsen burner. The component of the mixture with
the lowest boiling point will boil first, and its vapors will enter the column
labeled A. When these vapors first enter the
column, they are not very pure. The purpose of the column is to
improve the purity of these vapors. As the vapors come into contact
with the glass beads inside the column, the vapors condense and form droplets of
liquid. As more vapors move into the
column, these droplets of liquid heat up and turn into vapor again. This condensation and evaporation
cycle will repeat over and over as the vapors continue to move up the column. Each time evaporation repeats, the
vapors are more pure, until at the very top of the column the vapors will be the
purest.
The name of this column used in
fractional distillation is a fractionating column. The temperature of the vapors at
the top of the column is measured using a thermometer. The vapors then pass into the
condenser, where they are cooled, at which point they condense into a liquid and are
collected in the receiving flask. In conclusion, the name of the
piece of apparatus labeled A is a fractionating column, or answer choice (C).