Chemically Active Extraction

Summary

The 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

00:00

🧪 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.

05:01

🔬 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.

10:03

⚗️ 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.

15:04

🧊 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.

Keywords

💡Chemically active extraction

Chemically active extraction is the process of separating compounds based on their chemical reactivity. In the video, it refers to the method used to isolate acid neutral or base neutral compounds from an unknown mixture by adding specific reagents. This concept is central to the demonstration, as it shows how different reagents (like sodium hydroxide or hydrochloric acid) are used to extract specific components.

💡Acid neutral mixture

An acid neutral mixture is a combination of unknown compounds where acidic components have been neutralized or do not react as acids. In the video, students assigned an acid neutral mixture are instructed to follow specific steps, such as adding sodium hydroxide, to extract the compounds from the mixture. This term is crucial because it defines the type of extraction and reagents needed for separation.

💡Base neutral mixture

A base neutral mixture refers to a combination of compounds that have been neutralized or do not react as bases. In the video, students who receive this type of mixture must use dilute acid instead of sodium hydroxide to extract the components. The difference between acid and base neutral mixtures determines the procedures and flow diagrams students must follow.

💡Diethyl ether

Diethyl ether is an organic solvent commonly used in chemical extractions. In the video, it is used to dissolve the unknown mixture and facilitate the separation of compounds. The use of diethyl ether is highlighted during the steps where it is added to the mixture in the Erlenmeyer flask and later transferred into the separatory funnel.

💡Separatory funnel

A separatory funnel is a laboratory tool used to separate immiscible liquids, typically based on differences in density. In the video, it is used to separate the organic and aqueous layers after reagents are added. The stopcock on the funnel controls the release of the liquid, and students are instructed on how to carefully manage the layers to ensure proper separation of the compounds.

💡Sodium hydroxide

Sodium hydroxide (NaOH) is a strong base used in chemical extractions to react with acidic components in a mixture. In the video, it is added to the acid neutral mixture to create two distinct layers in the separatory funnel, allowing for separation. The use of sodium hydroxide is essential to extract the desired compound when dealing with acid neutral mixtures.

💡Aqueous layer

The aqueous layer refers to the water-based solution in a separation process, typically found at the bottom of a separatory funnel due to its higher density. In the video, the aqueous layer contains water-soluble compounds and is carefully drained during the extraction process. Its proper separation from the organic layer is vital to ensure that the right compounds are isolated.

💡Organic layer

The organic layer consists of the non-polar solvent, like diethyl ether, that contains the neutral, non-water-soluble compounds. In the video, the organic layer is at the top of the separatory funnel, and great care is taken to avoid mixing it with the aqueous layer. Proper extraction of the organic layer ensures that the neutral compound is isolated for further analysis.

💡Saturated sodium chloride

Saturated sodium chloride, or saltwater, is used to wash the organic layer in the extraction process. In the video, this wash helps to remove any residual water from the organic solvent, ensuring a purer separation of compounds. This step is critical for drying the organic layer before proceeding to isolate the neutral compound.

💡Calcium chloride

Calcium chloride is a drying agent used to remove water from organic solvents. In the video, solid calcium chloride is added to the ether layer to absorb any remaining water. Its effectiveness is checked by the free movement of calcium chloride balls at the bottom of the container. This step ensures that the ether layer is fully dry before the final extraction.

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