Scientific Method: Simple and Fractional Distilation Flashcards
What is the purpose of a distillation?
to separate and purify liquids
How does a distillation work?
it exploits the different boiling temperatures of two liquids in a mixture
liquid with lower boiling point
volatile
apparatus that the evaporated liquid will pass through first where it may be reverted back into a liquid
condensing column
Why is it important that cold water is passed through the condenser?
This allows for a gaseous liquid to recondense into its liquid form
What is the difference between a simple and fractional distillation set up?
A fractional distillation requires a fractionating column filled with glass beads to be placed between the boiling flask and the condensing column
What is the purpose of the glass beads in a fractionating column?
they provide “theoretical plates” on which the refluxing liquid can evaporate and condense on over and over, essentially redistilling the compound again and again.
Where do more volatile liquids rest in the fractionating column?
The more volatile liquid will tend to move higher up the column, while the less volatile liquid will remain towards the bottom. This provides a better separation between liquids.
When should a simple distillation be used
when the boiling point of two different liquids differ by 40 degrees or more
When should a fractional distillation be used?
when the boiling point of two different liquids differ by less than 40 degrees
What is the purpose of ethyl acetate (EtOAc) in the distillation experiment?
Ethyl acetate acts as the more volatile compound in the distillation
What is the purpose of n-butyl acetate (C6H12O2) in the distillation experiment?
N-Butyl acetate is the less volatile liquid (higher boiling point)
Why it important to grease each of the glass joints on the distillation apparatus?
A firm seal helps ensure that no heat or liquid is lost. It also helps ensure safety.
What is the purpose of each of the three collection flasks used in the distillation experiment?
- Flask A should house the majority of the distilled ethyl acetate
- Flask B should house the remainder of the distilled ethyl acetate and a small amount of n-butyl acetate when it begins to boil
- Flask C should house purely n-Butyl acetate
Why is it important that you do not use full voltage on the transformer?
It will heat the heating mantle too quickly, which will result in a poor separation of liquids
Why do we add boiling chips to the distillation pot?
The chips contain pores which allow excess air (bubbles) to be trapped, which allows for the liquids to boil smoothly without boiling over or loosing solution
Why is it important to record the temperature versus volume of distillate during the entire distillation?
This is to make sure that the heat and volume reflected at a certain time in the experiment will match up with the expected products in each flask.
Why are cork stoppers used instead of rubber stoppers?
Cork stoppers will not expand when under heat and pressure. Rubber will.
Why do we cover the fractionating column with aluminum foil in the fractional distillation?
This is to help insulate the column to keep heat in and air draft out.
What are the advantages of simple distillation?
- simpler set up than fractional
- faster distillation time
- consumes less energy than fractional distillation
What are the advantages of a fractional distillation?
- greater separation between liquids in comparison to simple distillation
- can more readily purify complex mixtures than simple can
What are the disadvantages of simple distillation?
- requires large boiling point difference between liquids
- gives poorer separation in comparison to fractional distillation
- only works well with relatively pure liquids
What are the disadvantages of fractional distillation?
- more complicated set up
- takes longer for liquids to distill
- consumes more energy than simple
What is a simple distillation best used for?
separating relatively pure liquids with large boiling difference or liquids with solid impurities
What is a fractional distillation best used for?
separating complex mixtures of liquids with smaller boiling point separations
What is A and what is its purpose?
heating mantle - used to slowly heat flask to each liquids respective boiling point
What is B and what is its purpose?
distillation flask/pot and boiling chips - used to house and boil liquids. Chips used to absorb bubbles.
What is C and what is its purpose?
Thermometer - tells temperature
What is D and what is its purpose
condensing column - runs cool liquid through it to recondense vapors
What is C and what is its purpose?
fractionating column - longer column used for better separation of vapors
What is D and what is its purpose?
glass beads - provides more surface area for vapors to condense and reevaporate on, further distilling the compound(s)
Steps of simple distillation
- set up glassware, making sure to grease glass joints
- place 2 liquids of equal volume into round bottom flask and attach to distillation apparatus
- use heating mantle and transformer for heat source
- place receiving flask A under tip of vacuum adapter and begin heating
- After every 10 drops, take a temperature reading and record.
- Switch to receiver B when thermometer hits 81*C and continue recording drops and temp (cork receiver A)
- Switch to receiver C when temp hits 123*C (cork receiver B)
- Stop recording when 1-2ml of liquid remains in pot or until plateau becomes clear.
what are the safety hazards of this experiment?
- ethyl acetate and n-butyl acetate fumes
- hot mantles
- USE A BOILING CHIP
- secure all the pieces as you build the distillation setup
