A 2.9 g sample of a caffeine/binder mixture was added to a 125mL Erlenmeyer flask and 50mL of water was added. The suspension was heated to boiling and the insoluble solid was removed by filtration. The aqueous filtrate was cooled and extracted with two 15 mL portions of dichloromethane. The combined organic layers were washed with 15 mL of a saturated sodium chloride solution and dried over anhydrous magnesium sulfate. The magnesium sulfate was removed by filtration and the organic layer was evaporated under reduced pressure to give 1.72g of white solid. The density of aqueous sodium chloride is 1g/mL and the density of dichloromethane is 1.3 gmL.

What was the percent composition of the original mixture? (Please show me the steps to get the answer. I already know the answer I just don't understand how to get to the answer)

Caffeine % = ???

Binder % = ???

answer

watching

views

For unlimited access to Homework Help, a Homework+ subscription is required.

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

Sixta KovacekLv2

13 Dec 2019

Unlock all answers

Get 1 free homework help answer.

Already have an account? Log in

Join us on Discord

Chemistry Study Group

Join now

Related questions

Separation of Acidic, Basic, and Neutral Compounds:

This is for an Ochem Lab. 1st-8th is just the steps of the procedure we followed and the question corresponds to the 8th step in the procedure;â In the first portion of the experiment, what is the purpose of washing the dichloromethane (layer C) with two 15 mL portions of water?

Background :

A mixture containing acidic, basic, and neutral compounds can be separated by acidic and basic properties. Commercial headache tablets, such as Excedrine, contain Aspirin (Acidic), Acetaminophen (Neutral), and Caffeine (Basic).

Procedure

1st)Weigh two headache tablets.

2nd)Crush using a mortal and pestle.

3rd)Dissolve the crushed tablets in 25mL of dichloromethane. Some solid binder may not dissolve so filter the dichloromethane using gravity filtration to remove the undissolved binder. This binder can be discarded.

4th)Transfer the dichloromethane solution to a separatory funnel and extract three times with 15 mL portions of 5% aqueous sodium bicarbonate.

5th)Combine the sodium bicarbonate layers in 100 mL beaker Labeled A.

6th)Extract the dichloromethane again but using three successive 15mL portions of 10% aqueous HCl.

7th)Combine the HCl layers in a beaker Labeled B.

8th)Lastly, wash* the dichloromethane with two 15mL portions of distilled water. The water will be the waste. Dry the dichloromethane over anhydrous calcium chloride. Label this C. 1.

If you were to run the experiment without using any celite, what would happen to the purity of your sample and why?

What practical purpose does the distillation serve in this experiment?

The experiment is below. Just answer the above questions.

Introduction Caffeine is one of three legal, mind-altering drugs available in the U.S without a prescription. Two common sources of this drug are tea and coffee, both of which are prepared via extraction of the solid foodstuff with liquid water. In this lab you will extract caffeine from food samples with liquid solvents and quantify the amount obtained. Laborator Hypothesis: We can rank various tea and coffee samples by caffeine content by performing a solid-liquid extraction from the foodstuff, followed by analysis via thin-layer chromatography. Experiment: In a 50 mL Erlenmeyer flask were placed 2.0 g of black tea. Dichloromethane (15 mL) and 0.2 M NaOH (5 mL) were added successively, and the stoppered flask was swirled gently by hand for 10 minutes (note: avoid vigorous shaking, as it will cause an emulsion to form). The dicloromethane layer was separated from the leaves and the aqueous layer by vacuum filtration through 7 g Celite 545, and the leaves were washed with a further 15 mL dichloromethane. The combined dichloromethane solution was placed in a 50 mL round bottom flask and concentrated to a minimal volume (ca. 1 mL) via simple distillation. The remaining dichloromethane solutions was transferred to a watch glass via pipet, and the solvent was evaporated in a fume hood. The sample was evaluated by TLC (a mixture of methanol and ethyl acetate as the mobile phase, co-spotted with authentic caffeine). Data: What was your crude yield of caffeine? What was the mass percentage of caffeine in your food source'? Given that the materials we are interested in are UV active, compared to the TLC standard how would you characterize the purity of your caffeine extracts? Conclusions: Can you comment on the purity of your caffeine sample? For all samples your class worked with where does your foodstuff rank in terms of caffeine content? How much caffeine is reported for the typical serving of coffee or tea? How did your extraction and isolation compare with the typical serving?

If you were to use THF, or tetrahydrofuran instead of dicholormethane for this experiment, could you still successfully extract your caffeine? Why or why not? (Consider what is necessary for an extraction to work)

If you were to use an acidic water solution for this extraction rather than a basic one, could you still perform the extraction?â

The experiment is below. Just answer the above questions.