Prelab for Experiment #2: Extraction
Your Name:
Lab partner’s name:
Name of TA:
Lab Section:
Title: Experiment #1: Extraction
Purpose: In this lab, we will partition materials between various solvents, based upon their
acid/base properties.
Reagents Table:
Name of Reagent
Biphenyl
Benzoic Acid
p-Nitroaniline
Methylene Chloride
3M HCl
3M NaOH
6M NaOH
6M HCl
M.W.
(g/mol)
154
122
138
85
M.P.
(oC)
70
122
146
B.P.
(oC)
39.8
Density
(g/ml)
1.32
Hazards
toxic
Contact hazard
poison
Carcinogen, toxic
Corrosive, Toxic
Corrosive, Toxic
Corrosive, Toxic
Corrosive, Toxic
Procedure:
1.
Weigh out 3 grams of the chemical mixture. Dissolve the mixture in 40 ml of CH2Cl2
with gentle heating. After all solids have dissolved, pour the solution into a separatory funnel.
2. Rinse the initial flask (used to dissolve mixture) with 10 ml CH2Cl2 and pour this solution to
the separatory funnel as well.
3. Add 15ml of 3M HCl and mix gently and vent. Allow the layers to separate and determine
which one is the organic layer. Collect the top (aqueous layer) in a container labeled HCl
extract. Place the lower organic layer into the separatory funnel and re-extract with another 15ml
of 3M HCl. Collect the aqueous extraction from the second extraction in the same container that
was labeled HCl extract. Keep this container (HCl extract) on ice. Once the HCl extract is cold,
add 6M NaOH dropwise till a precipitate is formed and red litmus paper turns blue. Chill solid
and vacuum filter solid followed by washing the crystals with chilled water.
4. Dry crystals and find the weight of p-nitroaniline. Do Not Recrystallize!
5. Place the lower organic layer once again in the separatory funnel. Add 15ml of 3M NaOH and
mix gently and vent. Allow the layers to separate and collect the top (aqueous layer) in a
container labeled NaOH extract. Place the lower organic layer back into the separatory funnel
and re-extract with another 15ml of 3M NaOH. Collect the aqueous extraction from this
extraction in the same container that was labeled NaOH extract. Keep this container (NaOH
extract) on ice as well. Once the NaOH extract is cold, add 6M HCl dropwise till a precipitate is
formed and blue litmus paper turns red. Chill solid and vacuum filter solid followed by washing
the crystals with chilled water.
6. Dry crystals and find the weight of benzoic acid
Take the remaining organic layer and add sodium sulfate until free floating salt is observed (~ 3
grams). Dry the organic layer for 5 minutes and filter the organic solution into a tared (preweighed) 100 ml round bottom flask. Remove the CH2Cl2 by rotary evaporator and find the
weight of biphenyl in the flask.
[This is the complete prelab for experiment 2. There are no prelab questions for this experiment,
so if you were to show up for the lab with this level of detail, you would be good to go!]
One other suggestion: you might want to use the columns in your lab notebook with one column
as Procedures and the next column as Observations:
Procedures
1. Weigh out 3 grams of the chemical
mixture
Observations
1. Weighed out 3.0148 grams of chemical
mixture.
2. Dissolve the mixture in 40 ml of
CH2Cl2 with gentle heating
2. Used 45 mL of CH2Cl2.