Chem Lab 3

Front 1

What is the title of exercise 3?

Back 1

Extracting caffeine from tea

Front 2

What is extraction?

Back 2

It is the technique used to separate a compound from a mixture.

Front 3

What are compounds?

Back 3

Compounds are substances that are chemically bonded

Front 4

What are mixtures?

Back 4

Are substances that are mixed physically

Front 5

What is a liquid-liquid extraction?

Back 5

It is the extraction technique involving two immiscible liquid solvents and a solute that we want to selectively dissolve from one solvent to the other. Generally, the solvents involved are water and a much less polar organic solvent.

Front 6

What does liquid-liquid extraction takes advantage of?

Back 6

It takes advantage of the differing solubilities of a solute to two different solvent in order to extract a compound.

Front 7

What is the apparatus used in liquid-liquid extraction?

Back 7

Separatory funnel

Front 8

What does the term salt indicate in chemistry?

Back 8

Compound that are ionic.

Front 9

What is solubility?

Back 9

It is the tendency of a compound to dissolve in a solvent. It is based on the polarity on the compound. Like dissolves like.

Front 10

What are intermolecular forces?

Back 10

These are attraction or repulsion between molecules because of dipole moments.

Front 11

How many extractions is enough for the separation of non-polar compounds?

Back 11

2 to 3

Front 12

How many extractions does polar organic compounds require?

Back 12

More than 3 or a different approach is needed.

Front 13

Give the formula that shows the distribution of the solute in the mixture.

Back 13

K = g compound per mL organic solvent / g compound per mL water (solvent)

Front 14

What is the k in the distribution formula?

Back 14

Distribution coefficient or partition coefficient.

Front 15

What does the distribution coefficient of 2 indicate?

Back 15

It indicates that the compound is much more soluble in the less polar organic solvent

Front 16

What is the first step in the third experiment?

Back 16

The bags of tea was opened and the tea leaves were weighed. After that, they were put back inside the tea bag.

Front 17

What does anhydrous mean?

Back 17

Substance with no water

Front 18

What is 2nd step of the experiment.

Back 18

The tea bags were put inside a 250 ml Beaker and mixed with 100 ml of water and 5 g of anhydrous calcium carbonate (CaCO3).

Cover the flask with a watch glass

Then we boil it on the hotplate for 10 mins

Front 19

What is the third step of the experiment?

Back 19

Decant the liquid into an Erlen Meyer flask. Then, add another 100 ml of distilled water to the tea bags and bring to boil again. Cool down and throw the.tea bags

Front 20

What is the 4th step of the experiment?

Back 20

We added 1.5 g of NaCl or salt to the mixture. Then we transfer it to a 25 ml separatory funnel.

Front 21

What is the 5th step of the experiment.

Back 21

10 milliliters of dichloromethane is added to the funnel (Ch2Cl2). Then, it is agitated. After that, the pressure inside the funnel is equalized by venting.

Front 22

6th step of the experiment.

Back 22

Let the contents of the separatory funnel to settle.

Front 23

7th step of the experiment

Back 23

Carefully drain the lower organic solvent.

Front 24

8th step of the experiment

Back 24

Repeat steps 5 through 7

Front 25

9th step of the experiment

Back 25

addition of 1 g of anhydrous sodium sulfate (NaSO4) to the dichloromethane mixture (Ch2Cl2) to remove excess water.

Front 26

10th step in the experiment

Back 26

Decant the water out of the mixture. Then, place the beaker in a hotplate set at 200 degrees and dry it in the steam bath. Calculate the percent recovery

Front 27

What is the percent recovery of the solute?

Back 27

% recovery = (weight of crude caffeine / weight of tea(l) )× 100 = 3.19 %

Front 28

What is the purpose of anhydrous calcium carbonate?

Back 28

It turns the tannin impurities into water-soluble products that won't dissolve to the organic solvent.

Front 29

What is the purpose of anhydrous sodium sulfate (NaSO4)

Back 29

It assimilates the water that is in the dichloromethane so that you can remove it by decantating the sodium sulfate clumps.

Front 30

What is the purpose of salt in the experiment?

Back 30

It increases the polarity of the aqueous layer to force all of the organic compound into the organic layer

Front 31

3 characteristics of dichloromethane that make it good solvent for extracting caffeine

Back 31

- caffeine has a higher solubility in dichloromethane than other solvents

- dichloromethane is insoluble with water

- dichloromethane is much more dense than water

Front 32

What are emulsions and how are they minimized during the extraction process?

Back 32

Emulsions are the temporary dispersion of immiscible compounds within one another. We minimize their formation by avoiding being too vigorous when we agitate the mixture.

Front 33

Why is it necessary to open the stopper when we drain the liquid through the stopcock?

Back 33

It is so that the liquid would flow smoothly because it generates a partial vacuum and opening the stopper balances the pressure within the separatory funnel and the atmosphere.

Front 34

Explain the process of venting

Back 34

Flip the separatory funnel until the solvent doesn't touch the stop cock. Open the stop cock to release the pressure. Then close it and agitate again.