Distillation

distillation

method of separation

one component in mixture must be?

liquid because it needs to be boiled in distillation

distillation method

take mixture, put in container, liquid vaporizes, collect vapor in separate container

simple distillation

most basic form, method to separate solid + liquids

vacuum distillation

lowers temperature of BP of liquid when it is really high, can also speed up experiment if there are a lot of solvent

fractional distillation

two liquids have boiling points that are within ~ 40 ºC

distallation system open or closed? why?

our distillation is open bc closed system heating is dangerous

why is our distillation open

because we do not have appropriate equipment and training

simple distillation for liquids

separate two liquids more than around 40 degrees C

distillation 50 mL flask

where solid remains

distillation head

- connect distillation flask to condenser

- connect thermometer

condenser

glass tube filled with water, water goes in at bottom and out at top

- cool vapor into liquid

thermometer

reads temperature

- will have rubber adaptor and glass adaptor

vacuum adapter

- connect condenser to receiving flask

- perform vacuum distillation, where hook up vacuum line

- keep system open

receiving flask

collect condensed liquid, also where you hook up vacuum adapter

liquid/solid T vs V graph

liquid/liquid (100 degrees C apart) T vs V graph

liquid/liquid (20 degrees C apart) T vs V graph

- will not be able to separate

- need fractional distillation

aluminum heating block

middle one fits 50 mL flask

lab jacks

lower/raise heating element w/o touching it

15 mL centrifuge tubes

collect different fractions

keck

holds glass joints so you can let go without it falling apart

aluminum foil

force heat into system

1 inch stir bar

want heat distributed evenly across solution

hose clamps

keep water hoses tight and closed

left side hood setup different because?

water hoses are cut to specific length, so want to make sure it reaches setup

- not heating hot enough

- turn heat up

- heating it too hot

- thermometer could not calibrate

2 questions want to answer

1) do we have acetone/toluene?

2) what is the ratio?

plateau on graph

shows BP of solvent

why there would be two plateaus

boiling point is a unique characteristic of each chemical so you can use this to identify which one you have in the mixture

difference between the plateaus

the first plateau is the lower BP liquid that eluted first; second plateau has a higher BP and this liquid eluted second

gas chromatography

method of separation based on attraction/polarity and boiling point (polar to polar/nonpolar to nonpolar)

2 phases of gc

stationary phase and mobile phase

stationary phase

polar

mobile phase

nonpolar

gc boiling points

lower comes out first, higher comes out second

gc very hot bc?

want to vaporize liquid into gas

flame ionization detector0

tells you chemical is here

more compound, what does peak area show?

higher peak area

qualitative analysis

retention time determines what chemical components are in a mixture

quantitative analysis

peak area determines the exact amount of a compound in a mixture

difference between simple and fractional distillation

fractional employs an additional vertical column between the distillation flask and the condenser

steel wool

maximize surface area and promote multiple iterations of condensation and vaporization as the vapor rises through the column

vertical column in fractional distillation

more gradual temperature gradient and leads to better separation when coupled with the increased number of theoretical plates bc longer distance between the distillation flask and the condenser

retention time

time that it takes a compound to elute from the column

why grease glass joints

fills air pockets with grease so solvent can't enter and increase pressure

put water at bottom of condenser because

filling up bottom wont have to turn pressure very high to fill the condenser up

clamps

hold distillation flask and distillation head

hold glass adapter with distillation head

hold distillation head with condenser

hold condenser with vacuum adapter

boiling point

the temperature at which the total vapor pressure of the liquid is equal to the external pressure

head temperature

temperature of the boiling liquid

dynamic equilibrium

the number of molecules in the gas phase will

initially increase until the rate at which they reenter the liquid becomes equal to the rate at which they escape from it

equilibrium vapor pressure

magnitude of this vapor pressure at a given temperature