Distillation

Question 1

What is the general concept of distillation?

Answer 1

Vaporize liquid > condense vapor > collect the vapor. This is used to separate liquids that have different boiling points.

Question 2

What is the definition of ‘boiling point’?

Answer 2

When the vapor pressure above a solution equals atmospheric pressure

Question 3

PA = vapor pressure of pure A. NA = mole fraction of A. What is the total pressure and the name of the law involved?

Answer 3

Raoult’s Law: Ptotal = PA*NA + PB*NB

Question 4

What is the general procedure?

Answer 4

1. Assemble distillation stuff 2. Water flowing through condenser, unknown mixture in round bottom flask, temperature up 3. Boil solution, watch condensation + dripping. Distillate should start after ~7min 4. Collect distillate, take temperature readings, take 2 samples for GC analysis

Question 5

Distillate

Answer 5

Distilled liquid (after vaporization > condensation)

Question 6

Things to remember: thermometer

Answer 6

-Keep thermometer bulb below joint -Make sure top is tightly sealed with O-ring holding thermometer in place

Question 7

Things to remember: condenser

Answer 7

-hoses pointing up -Water flowing in from bottom, out from top

Question 8

Things to remember: fractional distillation

Answer 8

-Grab PVC tubing, wrap around column to insulate

Question 9

How often to take temperature reading?

Answer 9

every 1/2ml

Question 10

When to take first sample for GC and how much to grab?

Answer 10

1ml distillate, grab 3-4 drops

Question 11

When to take second sample for GC?

Answer 11

5ml distillate

Question 12

What to do to prepare GC samples?

Answer 12

Fill vials to 1.5ml mark with dichloromethane

Question 13

How to get GC data?

Answer 13

Download it

Question 14

What is the VERY general procedure?

Answer 14

1. Boil out a solution into a flask 2. Collect temperature readings and 2 samples for GC analysis

Question 15

Components in distillation apparatus

Answer 15

-Hotplate/aluminum for eating, above which is a -10ml round-bottom flask with a couple boiling stones in it and the -Thermometer bulb lower than side-arm, inside a -Distillation head, connected to a -Clamp. Above the distillation head is a -Thermometer adapter with a -Thermometer inside (bulb below side-arm). On the right is a -Condenser (water out > water in) connected to a -Vacuum takeoff adapter, which sends distillate down to a -10ml graduated cylinder that stores distillate.

Question 16

What’s in fractional distillation apparatus that isn’t in normal?

Answer 16

Fractionating column with steel sponge packed inside and PVC tubing around it

Question 17

How much unknown mixture to add to flask?

Answer 17

8.0ml

Question 18

When to stop distillation? How to stop it?

Answer 18

When there’s only about 0.5ml remaining in the round-bottom flask. Turn off hot plate and raise the whole thing off the aluminum block.

Question 19

What data are we getting?

Answer 19

-Volume vs temperature graph -Printed chromatograph data with compound identities on it