1. Separating a Synthetic Pain Relief Mixture
AP Chemistry Inquiry Lab

2. Concepts Mixture vs. pure substance Physical/chemical changes
Separation of a mixture
Homogenous vs heterogeneous
Mass percent composition

3. Background A mixture is a combination of 2+ pure substances
The amount of each substance in a mixture can be changed, therefore the physical properties of a mixture will depend on its composition
Pure substances can be separated from their mixtures
Example: if one component in a mixture of two solids dissolves in water, while the second component does not, the substances can be separated by adding water o the mixture and then filtering the residue
Physical changes that can be used to separate the components of a mixture include: filtration, evaporation, crystallization, distillation, and extraction

4. Gravimetric Analysis
An experiment is carried out that yields a solid (often a precipitate) that can be dried and weighed. The mass can be converted to moles in order find out many other things via balanced chemical equations and molar relationships.

5. Based on immiscible (liquid- liquid) substances
Methods of Separation
Filtration, evaporation, crystallization, distillation, extraction
What is extraction?
Based on immiscible (liquid- liquid) substances
Use about 50 mL ethyl acetate and let sit for 5-7 minutes.

6. Extraction
Liquid-liquid extraction: a substance is at least partially soluble in two immiscible liquids can be transferred from one liquid to another.
It is done in a separatory funnel by shaking a solution containing two or more solutes with a second, immiscible solvent that will dissolve only one of the solutes
The liquids separate into two layers in the separatory funnel, with the more dense liquids in the bottom layer and the less dense liquid in the top layer

7. How to use separatory funnel
Close stopcock to ensure liquid will not spill.
Hold stopper when inverting the funnel to avoid having the stopper fall out when funnel is upside down.
Open stopcock to VENT excess pressure.
Repeat the shaking/venting process to ensure equilibrium distribution of the organic solute between the desired layers.

8. Flow Chart- used to illustrate steps involved in separating a mixture
Mixture of salt, sand, water
Filter to remove suspended solid
Solid (sand)
Liquid (salt and water)
Heat solution to evaporate water
Solid (residue- salt)
Water vapor (mass may be determined by difference)

9. Experiment Overview
The purpose of this lab is to separate a mixture that represents a pain reliever.
The mixture may contain binder (drug mixture to form pill, hold it together, and control the release of the drug in the body at varying rates), acetaminophen, and acetylsalicylic acid in varying amounts

10. Acetylsalicylic acid & Acetominophen
Acetylsalicylic acid is an organic carboxylic acid (has a --CO2H group) that contains an ester functional group (CH3CO2--) as a side chain on the benzene ring.
Acetaminophen has two primary functional groups, a hydroxyl group (-- OH) on the benzene ring , as well as an amide side chain (CH3CON—)

11. Acetylsalicylic acid & Acetominophen
Carboxylic acids that do not dissolve in water can be extracted from an organic solvent with an aqueous solution containing an inorganic base, such as dilute sodium hydroxide
The base converts the carboxylic acid to its conjugate base, a sodium salt that is soluble in water

12. Experiment Overview
In the introductory activity you will test the solubility of each possible component in an organic solvent, ethyl acetate, and in a basic aqueous solution of sodium bicarbonate.
The results will provide a model for the guided- inquiry design of a flow chart that will map the procedure used to separate components in a mixture and determine percent composition

13. Mass Percent
Used to express the actual composition of a mixture in terms on the amount of each component
% composition = (mass of component/ mass of mixture) x 100%

14. Pre-Lab Questions
(1) The Department of Transportation uses a mixture of sand and salt to de-ice roadways in the winter. The mixture contains 8.35 tons of salt and 6.28 tons of sand. What is the mass percent of each component in the mixture?
(2) A bakery needs a mixture of flour and sugar to make cookies. The mixture should contain 62.5% flour and 37.5% sugar. You are in charge of ordering the components to make 275 pounds of the mixture. How many pounds of flour and sugar should be ordered?
(3) In the Introductory Activity, the solubility of the possible components in the synthetic pain relief mixture will be tested using a 10% sodium bicarbonate solution. Is the solution acidic or basic? What is the likely pH of the sodium bicarbonate solution?
(4) Predict which component in the synthetic pain relief mixture is likely to dissolve in sodium bicarbonate solution. Explain.

15. Answers

16. Materials Acetaminophen, C8H9NO (10 mg)
Acetylsalicylic acid, C9H8O3 (10 mg)
Ethyl acetate, CH3CO2CH2CH3
Hydrochloric acid, HCl (6 M)
Silica gel
Sodium bicarbonate solution (NaHCO3, 10%)
Synthetic pain relief mixture
Balance
Beakers
Boiling stones
Capillary tubes
Erlenmeyer flask
Filter paper
Funnel
Graduated cylinder
Hot plate
Ice bath
Stirring rod
Magnetic stir bar
pH test strips, 3
Separatory funnel, 250-mL
Spatula
Support stand and ring clamp
Test tubes, 5
Watch glasses, 2
Weighing dishes

17. Introductory Activity
1. Obtain small, quarter-pea-size amounts (1-2 mg each) of acetylsalicylic acid, acetaminophen, and silica gel in separate labeled test tubes
2. Add 1 mL of ethyl acetate to each test tube, stir and record observations
3. Add 1 mL of deionized or distilled water to the three test tubes containing ethyl acetate and dissolved or undissolved solids. Record all observations.
4. Obtain additional 1-2 mg samples of acetylsalicylic acid and acetaminophen in separate clean and labeled test tubes. Add 1 mL of 10% sodium bicarbonate to each test tube and record observations.
5. Slowly and carefully add about 1-2 mL of 6 M hydrochloric acid drop-wise to the test tube mixtures from step 4. Record observations. Place test tubes in an ice bath for 5 minutes and record any additional observations.

18. Sample data for Intro Activity:
Acetaminophen and acetylsalicylic acid BOTH dissolve in ethyl acetate with vigorous mixing.
The binder (silica gel) does NOT dissolve in ethyl acetate
Water is not miscible in ethyl acetate
Water layer is more dense (it is at bottom of test tubes containing acetaminophen and acetylsalicylic acid solutions)
Acetaminophen does NOT dissolve in sodium bicarbonate
Acetylsalicylic acid DOES dissolve in sodium bicarbonate sol’n w/vigorous mixing
There is a lot of bubbling and a precipitate may fall out of solution when acid is added to the sodium bicarbonate/acetylsalicylic acid mixture

19. For Homework tonight:
After your data table, you will answer “Guided Inquiry Design and Procedure” #1-9 in your lab notebooks. You may photocopy and paste the questions in if you’d like. For your answer to question #9 (create a flow chart), please complete on a separate sheet of paper as corrections may be necessary.
Please get out a blank sheet of paper.

20. Here is step 1 of the flow chart (#9 from guided inquiry questions) Obtain the necessary supplies and get this done today!
450 mg pain relief mixture = g
Materials (not all will be used today):
0.450 g sample mixture
mL beakers
150-mL beaker
600-mL beaker (for ice bath)
2 Gooch crucibles
Erlenmeyer flask
Stir Bar
Glass stir rod
Separatory funnel
50-mL graduated cylinder
Utility clamp
Ring stand
Add about 30 mL ethyl acetate into a 250-mL beaker; stir rigorously with a magnetic stir bar (and stir function on hot plate) for 5-7 minutes. Filter into an Erlyenmeyer flask using a Gooch crucible.
Acetaminophen
Acetylsalicylic acid
Transfer solution to a separatory funnel. Add 25 mL of 10% NaHCO3. Shake and vent.
Binder
Stay tuned for some lab hints when you’re done copying all of this down and obtaining your supplies…

21. Lab Hints:
Take the mass of gooch crucible before filtering. Let the ethyl acetate solution dry overnight; you can account for the silica gel this way, without having to scrape it out and possibly lose some in the process.
Take the mass of your 250-mL beaker before adding in mixture or ethyl acetate. There may be some silica gel left over after pouring mixture through gooch crucible, so if you let the beaker dry overnight, you can account for the leftover silica gels mass
Take the mass of the 2nd gooch crucible as well so that after filtering and drying the acetylsalicylic acid, you can account for it the same way.
Take the mass of the 2nd 250-mL beaker as well so that after drying the acetaminophen, you can account for it the same way.

22. Materials (not all will be used today):
0.450 g sample mixture
mL beakers
150-mL beaker
600-mL beaker (for ice bath)
2 Gooch crucibles
Erlenmeyer flask
Stir Bar
Glass stir rod
Separatory funnel
50-mL graduated cylinder
Utility clamp
Ring stand

23. (4)
C9H8O4 + NaHCO3  C9H7O4Na (aq) + H2CO3(aq)
C9H7O4Na + HCl  C9H8O4 + NaCl (put in ice bath and acetylsalicylic acid will precipitate)

24. 450 mg pain relief mixture = 0.450 g
Add about 50 mL ethyl acetate into a 250-mL beaker; stir rigorously with a magnetic stir bar (and stir function on hot plate) for 5-7 minutes. Filter into an Erlyenmeyer flask using a Gooch crucible.
Binder
Acetaminophen
Acetylsalicylic acid
Transfer solution to a separatory funnel. Add 25 mL of 10% NaHCO3. Shake and vent.
Transfer aqueous layer (bottom/dense layer) to 150- mL beaker
Acetaminophen
(organic layer)
Acetylsalicylic Acid
(aqueous layer)
Add 25 mL 10% NaHCO3 to the separatory funnel (repeating previous step to ensure complete separation of remaining mixture)
Combine aqueous layers in the 150-mL beaker
Acetylsalicylic Acid
(combined aqueous layers in the beaker)
Acetaminophen
(organic layer)
Add 25 mL 6 M HCl and place beaker in ice bath (use a larger beaker for ice bath) with a magnetic stirrer in the 150-mL beaker for a few minutes and then filter in gooch crucible
Pour into 250-mL beaker and
evaporate overnight
Acetaminophen
Acetylsalicylic acid
Aqueous waste