Chemically Active Extraction
Summary
TLDRThe video demonstrates the process of chemically active extraction, focusing on acid-neutral and base-neutral mixtures. The procedure involves using diethyl ether to extract and separate unknown compounds, followed by washing with sodium hydroxide or acid, depending on the mixture. The separatory funnel technique is utilized to distinguish between aqueous and organic layers. The organic layer is dried using sodium chloride and calcium chloride, then filtered. The final steps include isolating the neutral unknown compound through steam distillation and precipitating the unknown acid or base for further analysis. Emphasis is placed on accurate documentation in the laboratory notebook.
Takeaways
- 🔬 The laboratory exercise involves performing a chemically active extraction of an unknown compound mixture that is either acid-neutral or base-neutral.
- 📝 It is crucial to record the number of the unknown mixture in the laboratory notebook, whether it's a paper or electronic version.
- 🧪 Dr. Amenta demonstrates the acid-neutral extraction process, which includes mixing the unknown sample with diethyl ether and transferring the mixture to a separatory funnel.
- ⚗️ Ensure the complete transfer of the unknown sample by rinsing the test tube with diethyl ether multiple times to avoid losing any material.
- 🔧 When using the separatory funnel, always close the stopcock before adding any liquids and vent periodically during shaking to release pressure.
- 💧 The extraction involves separating an aqueous layer (bottom) and an organic layer (top), with sodium hydroxide added to react with the acid.
- ❄️ After multiple extractions, the combined aqueous layers are placed in an ice bath for further processing while the organic layer is dried using calcium chloride.
- 🧊 The organic layer is further purified using a saturated sodium chloride wash, and then dried using calcium chloride before isolating the neutral compound.
- 🔥 A steam bath is used to remove the ether from the organic layer due to ether's low boiling point and flammable nature.
- 📝 It is important to check the litmus paper to confirm the solution's acidity and record all details about the unknown mixture in the laboratory notebook.
Q & A
What type of extraction is being performed in the laboratory?
-The laboratory is performing a chemically active extraction, specifically either an acid-neutral or a base-neutral mixture extraction, depending on the unknown mixture assigned to the student.
What should students ensure to record before starting the experiment?
-Students should ensure to record the number of their unknown mixture in their laboratory notebook, either in a paper copy or electronic version.
What solvent is used to help transfer the mixture from the test tube to the Erlenmeyer flask?
-Diethyl ether is used to help transfer the mixture from the test tube to the Erlenmeyer flask.
Why is sodium hydroxide added to the unknown mixture?
-Sodium hydroxide is added because the demonstration is for an acid-neutral mixture. It reacts with the acid component to form an aqueous layer.
How can you tell the difference between the aqueous and organic layers in the separatory funnel?
-The aqueous layer will be at the bottom, and the organic layer will be at the top. Sometimes it's difficult to see, so placing your hand behind the separatory funnel can help identify the interface.
Why is it important to vent the separatory funnel during shaking?
-Ventilation is important to release any pressure that builds up during shaking, preventing any accidents from over-pressurization.
What is the purpose of adding saturated sodium chloride to the organic layer?
-Saturated sodium chloride is added to wash and further separate the organic layer from any remaining aqueous components.
Why is solid calcium chloride added to the organic layer?
-Solid calcium chloride is added to dry the ether layer by absorbing any water that may still be present.
How can you tell when the ether has completely evaporated during the steam bath process?
-You can tell the ether has completely evaporated when there are no more bubbles forming and the mixture stops boiling. Ether has a low boiling point, so once it evaporates, only the unknown liquid with a higher boiling point will remain.
What is the final step for the unknown neutral compound after evaporation of the ether?
-The final step is to transfer the neutral unknown into a pre-weighed round bottom flask for storage, ensuring that no liquid is lost during the transfer.
Outlines
🧪 Introduction to Chemically Active Extraction
In this lab, students will conduct a chemically active extraction. Depending on their assigned mixture, which is either acid-neutral or base-neutral, they will record the mixture number in their lab notebook. This documentation is essential for tracking the mixture. The demonstration focuses on an acid-neutral extraction, with guidance for those handling a base-neutral sample to refer to their flowchart. Dr. Amenta begins the demonstration with an unknown mixture containing both solid and liquid components, though not all samples will contain solids. The goal is to perform an active extraction to separate the components.
🔬 Preparing the Extraction Process
Dr. Amenta uses a glass stirring rod to mix the components and transfers the mixture to an Erlenmeyer flask. Some material sticks to the test tube, but this is remedied by rinsing it with diethyl ether, which is measured to approximately 100 mL. The ether is added to the flask, with a beaker acting as a lid to prevent evaporation. Ensuring all material is transferred from the test tube to the Erlenmeyer flask is crucial. The separatory funnel is then prepared, making sure the stopcock is in the closed position. After transferring the mixture, sodium hydroxide is added to separate the layers.
⚗️ Layer Separation and Proper Venting
After adding sodium hydroxide, two layers form in the separatory funnel: an aqueous layer at the bottom and an organic layer at the top. Dr. Amenta demonstrates how to invert the funnel, venting periodically to release pressure while shaking the mixture. She carefully drains the aqueous layer and repeats the sodium hydroxide addition, always ensuring that the layers are correctly separated and transferred to the appropriate beakers. The final step involves a careful and slow drain of the last aqueous layer to avoid contamination with the organic layer.
🧊 Preparing for Further Extraction Steps
After combining all aqueous extractions into one beaker, it is placed in an ice bath to prepare for the next steps. The organic layer, which contains the neutral unknown, remains in the separatory funnel. To dry the organic layer, saturated sodium chloride is added, followed by shaking and venting. The aqueous layer is drained into the waste beaker, ensuring the organic layer remains free of water. Dr. Amenta ensures that no water is trapped in the organic layer by carefully draining the separatory funnel.
🧴 Drying the Organic Layer
The ether layer, which contains the neutral unknown, is poured out of the separatory funnel into a clean, dry Erlenmeyer flask. Solid calcium chloride is added to the ether layer to absorb any remaining water. Dr. Amenta stirs the mixture to ensure proper drying, noting that if the calcium chloride clumps, more should be added. The dried ether layer is then filtered using a cotton ball and transferred to a beaker labeled 'organic.' This step ensures the separation of the organic unknown from any remaining impurities.
🔥 Using Steam to Isolate the Organic Unknown
Dr. Amenta demonstrates the final isolation step by using a steam bath to evaporate the ether from the organic unknown. The steam bath is prepared by draining the steam line to remove water, then attaching the hose. A boiling stick is placed in the organic layer to facilitate the process. As the ether evaporates, Dr. Amenta explains that students should wait until boiling stops, which indicates the ether is fully removed, leaving behind the isolated organic unknown.
🥶 Precipitation of the Acid or Base Unknown
Dr. Amenta proceeds to recover the acid unknown by adding concentrated hydrochloric acid dropwise to the solution in the ice bath. A precipitate forms as the acid reacts with the unknown, and the process continues until no more precipitate forms. The acidity is confirmed using litmus paper, which turns red when the solution is sufficiently acidic. The mixture is then allowed to sit briefly in the ice bath while the organic extraction completes.
📝 Final Separation and Storage of Compounds
The organic layer, now free of ether, is transferred to a pre-weighed round bottom flask for storage. The remaining solid acid or base unknown is either suction filtered or transferred to a pre-weighed Erlenmeyer flask, depending on whether it is an acid or base. For base unknowns, the flask is corked to prevent sublimation. After these final steps, the separation of the unknown mixture is complete. The video concludes with a reminder to record the unknown number in the lab notebook.
Mindmap
Keywords
💡Chemically active extraction
💡Acid neutral mixture
💡Base neutral mixture
💡Diethyl ether
💡Separatory funnel
💡Sodium hydroxide
💡Aqueous layer
💡Organic layer
💡Saturated sodium chloride
💡Calcium chloride
Highlights
Students are assigned either an acid-neutral or base-neutral mixture of unknown compounds for extraction.
It is essential to record the mixture number in your laboratory notebook for identification.
Dr. Amenta demonstrates an acid-neutral active extraction with a mixture containing both solid and liquid components.
Diethyl ether is used to rinse and transfer the unknown mixture, ensuring a complete transfer into the separatory funnel.
When performing the extraction, two layers form: an aqueous layer on the bottom and an organic layer on top.
Sodium hydroxide is added to the mixture in three additions to separate the layers during an acid-neutral extraction.
Proper shaking and venting are necessary to avoid pressure buildup in the separatory funnel during extraction.
Sodium chloride wash is used to dry the organic layer, followed by calcium chloride to further remove moisture.
The organic layer, containing the neutral unknown, is transferred into a clean, dry Erlenmeyer flask.
The ether layer is evaporated using a steam bath, ensuring no boiling remains once the solvent is fully removed.
The acid or base unknown is recovered from the aqueous layer by adding 12 molar HCl to precipitate the unknown.
Students are reminded to use litmus paper to confirm the presence of acid or base during the separation process.
Once the extraction is complete, the neutral unknown is stored in a pre-weighed round-bottom flask for later analysis.
Unknown acids or bases must be suction filtered and stored appropriately, depending on their sublimation properties.
A final reminder is given to record the unknown number in the laboratory notebook to ensure accurate tracking of the experiment.
Transcripts
this week in the laboratory you'll be
performing a chemically active
extraction
you should have been assigned either an
acid neutral
or a base neutral mixture of unknown
compounds
this mixture will have a number make
sure to record this
in your laboratory notebook whether that
be a paper copy
or the electronic version this is
essential
as this is the way we know what mixture
you have
in this demonstration we will be doing
an acid neutral
active extraction if you have a base
neutral sample
make sure to refer to your own flow
diagram
to ensure that you are adding the
correct reagents
throughout the extraction dr amenta has
obtained her unknown mixture
that has a solid component and a liquid
component
however from our discussions we know
that not everybody will see a solid
some of these substances may be miscible
and so we're going to perform an active
extraction to separate the two
dr minta is using her glass stirring rod
to mix up the two
and is then pouring the mixture into a
clean
125 erlenmeyer flask
you'll notice that some of the solid
gets stuck along the beaker or sorry the
test tube
that is not a big deal as we're going to
rinse this test tube with diethyl ether
in your flow chart you have noted that
you need to add 100 ml
of diethyl ether to your unknown mixture
dr amenta is going to measure this into
a graduated cylinder
and again this does not need to be a
very precise measurement
as long as you're close to 100 that will
be perfect
while you're storing this ether in the
erlenmeyer flask it's handy to have a
beaker around
to use as a lid in case this evaporates
perfect now dr ament is going to add
some of the diethyl ether to the
erlenmeyer flask
but first she's going to add some to her
test tube that contain the mixture
this is to ensure that all the material
gets completely transferred
she again can use her stirring rod to
mix everything up
in an attempt to get everything
dissolved
note that some mixtures may be more
soluble than others
but you really want to make sure that
you get all of the material
out of that test tube
here she goes for another rinse of the
test tube
in order to get that complete transfer
to the erlenmeyer plus
once your test tube is completely
cleaned out
and into your erlenmeyer we want to get
our separatory funnel prepared
you'll notice in your separatory funnel
that the stopcock has two
positions off
and on
you want to have the stopcock in the
closed position
before you add any of your mixture to
the separatory funnel
we also have a beaker that's labeled as
waste
underneath when you put your separatory
funnel
in the ring it should hold it nicely and
you should have the tip of the
separatory funnel
well into the waste beginner we're then
going to use
the small diameter short funnel to
transfer
our mixture that's dissolved in ether
into our separator pump
we still have this 100 milliliters of
ether so again to ensure a complete
transfer
we're going to add ether to that
erlenmeyer flask
and give it a nice swirl to ensure that
all of our unknown compounds
are making it into the separatory funnel
now ready to add sodium hydroxide to our
unknown mixture
this is because we have an acid neutral
if you have a base neutral mixture you
will need to add
dilute acid at this stage we're going to
add
10 sodium hydroxide 15 milliliters
over three additions we're using the
short
liquid funnel to do the transfer here
when you do this addition you'll notice
that now we have
two layers in our separatory pump
you can see that there's two layers an
aqueous layer
on the bottom an organic layer on the
top
at this point dr amenta is going to put
the stopper
in her separatory funnel she's going to
put her fingers around the stopper
and invert the separatory funnel she's
then going to
open the stopcock to release any
pressure
once she closes the stopcock she's going
to give it a really great shape
and during that she will vent
periodically to ensure that there's no
pressure build up
in her separatory pump you want to do
a couple cycles of shaking and venting
to ensure
that your acid is reacting with this
dilute base
we now put the separatory funnel back
into the ring
and we're again looking for these two
layers where the aqueous layer
is on the bottom and the organic on the
top
and sometimes it can be hard to see that
interface you may need to use your hand
behind the separatory funnel to see the
organic aqueous interface
with the stopper removed and the aqueous
base speaker placed below
you want to slowly open your stop cup
you'll notice that dr amenta didn't just
keep it open the entire time
she drains a small amount and looks for
her layer to ensure that there's no
aqueous layer
sticking to the sides of her separatory
funnel
as you get closer to getting your
complete layer down
we can use very small turns of the
stopcock
you're really trying to get it down so
that your layer is trapped
inside the stopcock if you're nervous on
this first edition
don't worry because you're going to add
some more sodium hydroxide
to your class dr amenta is now on her
third edition
of 15 milliliters of dilute base
[Music]
you'll notice that every time she does
an addition she trades
her layer beaker for the waste beaker
just in case
there's an issue with the transfer or
the stopcock accidentally gets open
she'll now for the last time trade the
stopper
and really make sure she pushes it down
while she's shaking it
again remembering to vent but really
pushing that stopper down
in order to make sure there's no leakage
from the top
of the separatory one she will shake and
vent
in several cycles here and then do a
final drain
to isolate her aqueously
during the last extraction you really
want to be careful while draining your
aqueous layer
into the beaker do this slowly to try
and avoid
too much water being dissolved or
miscible with your organic lamb
this will save you trouble during the
next portion of the extraction
you'll also note that again dr amenta is
trying to trap the interface
inside the softpot to ensure that she
collects
all of her aqueously perfect job
we now have all three combined aqueous
extractions
in the one beaker labeled aqueous we're
now going to place that
into the ice bath while we do the next
portion of the extraction
this beaker again contains your unknown
salt of your acid or base depending on
which you had
is your unknown we're now going to dry
our organic layer and we're going to
start off by adding
saturated sodium chloride
our organic layer has just remained in
the separatory funnel
dr amenta is going to do one wash with
the saturated sodium chloride
using about 20 milliliters
[Music]
we want to make sure that we now have
our waste beaker
underneath the separatory funnel as this
wash with sodium hydroxide or sorry
sodium chloride solution does not
contain
either of our desired unknown products
again we're going to see two phases
and an interface between the aqueous and
organic layers
just like our previous methods we're
giving this a great shake
making sure to push down on the stopper
and periodically vent
this extraction
dr amenta is removing the stopper and
just as a quick tip
sometimes you open your stopcock and
you'll say
nothing's coming out of my separatory
funnel check to make sure your stopper
is removed as if you keep your stopper
in the separatory funnel
you will form a vacuum and your liquid
will not drain out the bug
we're now going to drain the aqueous
layer into the waste speaker
in an attempt to dry our ether layer
remembering that our ether layer has our
neutral
unknown contained within it detriment is
again being careful
and slowly turning the stopcock in
incremental
segments in order to make sure no water
gets trapped within our either way
we are looking for that interface to
again be trapped within the stockpile
almost there
[Music]
excellent work now we need to get
our ether layer out of the separatory
funnel we do not want to drain this
through the stopcock
we do however want to pour it out the
top into a new
clean dry 125 erlenmeyer class
we're now going to take an additional
step to dry our ether layer
by adding solid calcium chloride to our
ether layer
this can be done with your scoopula once
you've added some of the calcium
chloride be sure to put the lid back on
as it absorbs water very easily you then
want to swirl your ether layer
and you're looking for the balls of
calcium chloride
to flow freely on the bottom if they
clump together
that means that they've absorbed water
and they will not unclump you have to
add
more calcium fluoride in order to
continue the drying process
[Music]
we're now ready to filter out our
calcium chloride by putting a small
cotton piece inside the wide funnel
we've just taken a cotton ball and
ripped a piece of that cotton off you do
not need to use a full cotton ball
we're then going to decant our ether
layer which has been dried over the
calcium chloride
into a beaker that's labeled organic
it is okay if some of the calcium
chloride comes over though you're trying
to keep the majority of it
in your erlenmeyer fly but that's what
the cotton is there for
[Music]
excellent work doctor
now we're ready to isolate our organic
unknown we're going to isolate this by
using a steam bath
but the first thing we need to do is
drain the steam line
this is done by using a bat that we
would use to get ice
and opening the black steam vent
water will come out as it condenses
within the line
and we want to drain this until water
stops coming out
and you get pure steam you may still
have a little bit of water that comes
out during the steam process
and that's okay we just want to get the
bulk of the water
out of the line
all right once you have steam going you
want to turn this off
so that you can put down your bath and
attach
the hose to your steam bath
you then want to put a boiling stick
in your organic layer
and turn the steam back on
you want to be careful here that you do
have a good amount of steam going
but that it's not going too crazy
and condensing water back into the dried
ether layer
ether has a low boiling point and is
also quite flammable
which is why we're using a steam bath to
avoid any sparks that may come
from our typical hot plate so we've just
started boiling
how do i know when i'm done how do you
know when you're done
a very common question that gets asked
in this laboratory
if you refer back to your unknown sheet
you will see
that all of the unknown neutrals have
boiling points
well over 100 degrees c if this is the
case
then we should not see any more boiling
once the ether is gone
since we're using steam to remove the
excess solvent
so when your mixture stops boiling you
can be confident
that you've isolated your unknown liquid
we're getting close to the point where
we're nearly done removing all of the
ether
but you can see that we still have a few
bubbles going
be patient and make sure until there is
no longer
little bubbles at your boiling stick or
on any other portion of the pizza
the salt of our unknown acid has been
sitting in the ice up
and in order to get our acid unknown
back out
we're going to be adding 12 molar hcl
via dropper bottle if again
you have an unknown base you would want
to be adding concentrated sodium
hydroxide
to the solution at this point so dr
amenta is going to use her stirring rod
and add dropwise
for strong acids
as you continue to drop you may start to
see the formation of a little bit of
solid
that disappears you want to continue
adding your concentrated acid until the
solid persists
we're also going to check it with litmus
basically
as you start to see dr amenta is seeing
some solid
in her beaker but she's going to
continue to add acid
until no more new precipitate if you can
hear what you think
when no more new precipitate forms you
can see she has a nice white frothy
mixture in here
and she's going to use her stirring rod
to dip into solution and then on to the
litmus
we're looking for blue litmus to turn
red
looking like acid to me at this point
you just want to make sure that your
mixture
um is nice and swirled
that you don't have too much solid
sticking to the side
and you just want to let this sit
momentarily in the ice bath
if we look back to our organic we can
see that there are no more bubbles
and you can also see we're starting to
get some vapor on the side or it's
starting to do
almost a little bit of a distillation so
at this point we're going to remove it
from the heat
and we're going to transfer our neutrals
into a 25 milliliter round bottom flask
that's been pre-weighed we want to make
sure that we get
all of our liquid as we work very hard
to separate
it
sometimes you can tilt the beaker just
to make sure it's easier to remove that
last little bit
from your beaker
you then want to put your glass stopper
on put your
your round bottom clasp in a beaker and
make sure it has your initials
or your name on it we will then store
these in the refrigerator
or in your tray at this point you've
successfully separated
your unknown mixture you have your
liquid neutral unknown
in the round bottom flask and you will
have suction filter
your unknown acid or base at this point
if you have an unknown acid you want to
transfer that acid to a pre-weighed
weibo or paper boat if you have
an unknown base you want to transfer
your from your filter flask into a dry
pre-weighed 125 milliliter
erlenmeyer flask that we are then going
to cork
this is because some of the unknown
bases sublime
and we wouldn't want you to lose your
compound after you did
all this hard work in your separation
this completes chemically active
extraction
we hope that this video gives you
confidence while using your own flow
diagram that you developed
for your extraction of either your acid
neutral or base neutral
unknown mixture with one final reminder
to please write down your unknown number
in your laboratory notebook
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