Question

Would the methylene chloride layer be above or below the experiment? Justify your answer. 1. aqueous layer in today's ium carbonate used in the isolation of caffeine? Be specific as to the 2. Why is potass chemical species the carbonate may act on. Why was sodium sulfate used? 3. 4. After introducing 1.0 g of potassium carbonate into the centri hot water extract, it was capped, shaken, and then cooled to room temperature. Following this, roug minute. Why wasn't the dichloromethane placed in the centrifuge tube with for one the carbonate and the warm extract in one step? Hint: Check the boiling points Where do the carboxylic acids end up? 5. Define sublimation. Explain, using a phase diagram. 6. Why is it important to add ice water to the cold finger after the vacuum has been turned on in your sublimation apparatus? 7. 8. Draw and label the parts of a sublimation apparatus 9. Draw an approximate phase diagram for caffeine. Label the axes and the phases (g). (I), and (s). Indicate the phase changes: sublimation, deposition, evaporation, con- densation, melting, and freezing. Explain why we use vacuum for the sublimation. 10. If a cup of tea (100 mL) contains 40 mg of caffeine, what is the molar concentration of caffeine in tea? Procedure Weigh out approximately one gram of the dimethoxybenzene/benzoic acid mixture into a small Erlenmeyer flask. Obtain about 45 mL of diethyl ether (usually referred to as just ether), and cool the ether in an ice bath for a few minutes. Use a small amount of the cooled ether to dissolve the mixture, and transfer the resulting solution to a separatory funnel. Continue rinsing the small Erlenmeyer flask using the rest of the cooled ether. combining all of the ether rinses in the separatory funnel. Add about 10 mL of cooled 0.5 N sodium hydroxide solution to the separatory funnel, and shake the mixture in the rmanner. The benzoic acid will react with the base and form the water-soluble nzoate anion C H.COO°) Draw off the aqueous phase (on the bottom because water is denser than ether) into a 125 ml Erlenmeyer flask, and add a second, fresh 10 ml. portion of chilled sodium hy- droxide solution to the ether solution in the separatory funnel. Shake again to remove any traces of benzoic acid which might remain in the ether. Shake well as before, draw off the aqueous phase, and combine it with the first portion. This is called successive extraction and when performing such, you should always combine the like fractions. The neutral dimethoxybenzene now remains in the ether layer, and the benzoic acid has been transferred to the aqueous phase. To asure that all traces of the base (NaOH) are gone, extract the ether layer with 10 ml of cooled, deionized water, and add this to the other aqueous extracts The ether layer is poured from the top into a dlean, dry labeled. 250 ml. Erlenmeyer fask NOTE: Although it might seem more sensible to drain the ether through the stopcock, water trapped in the stopcock bore and clinging to the walls of the funnel will also drain out, requiring the use of larger amounts of drying agent later Dry the ether layer by ading anbydrois sodium sulfate to the solution and swirling the Dry mixture until some loose, unclumped crystals remain. Stopper the flask and set it aside. The aqueous phase should now be acidified in order to regenerate the benzoic acid. After washing the separatory funnel well with water, pour the aqueous phase separatory funnel, and add about 5 mL of cooled 3 M hydro-chloric acid. Check the pH of the solution with pH paper after the addition to be sure that it is acidic; if it is not, add more acid-a few drops at a time-until the test paper indicates the solution is acidic. A white precipitate of benzoic acid, which is insoluble in water, should have formed at this back into the point

Answer 1

Dichloromethylne layer would be below aqueous layer.

Dichloromethylne (CH2Cl2) or methylene chloride is also called as DCM (organic layer). It has density of 1.33 g/cm³ and the density of water is 1gm/cm³. In separatory funnel when both organic (DCM) and aqueous layers (water) are combined, being denser Dichloromethylne layer would sink to the bottom or below the aqueous layer. The aqueous layer would be at top because of lower in density.