Extraction Question Set: Using a mixture with equal proportions of naphthalene, benzoic acid, and 2-naphthol.
1. You dissolve 6 g of a mixture in 60 mL of ether and transfer the mixture to a separatory funnel using little ether to complete the transfer. Add 20 mL of water to the separatory funnel. Which layer is the organic layer and which is the aqueous layer?
2. Then you add 20 mL of a 10% solution of sodium bicarbonate to the separatoryfunnel, stopper and cautiously mix the contents. Vent the liberated gas and shake the mixture vigorously with frequent venting. What gas is liberated in the funnel? Write an equation to show the formation of this gas.
3. You allow the layers to separate completely and then draw off the aqueous layer into Flask #1. What compound does this aqueous layer contain? In what structural form does this compound exist in the solution in Flask #1?
4. Next you add 20 mL of 5% aqueous sodium hydroxide to the separatory funnel, shake the mixture thoroughly, allow the layers to separate and draw off the aqueous layer into a 50-mL flask (Flask #2). You add an additional 10 mL of water to the separatory funnel, shake the mixture, separate layers and add the aqueous layer to Flask #2. What compound does Flask #2 contain?
5. You add 30 mL of a saturated solution of sodium chloride to the funnel and shake the mixture thoroughly. Allow the layers to separate, then draw off the aqueous layer and discard it. What is the purpose of adding the saturated sodium chloride solution?
6. You carefully pour what is left in the separatory funnel into a 100 mL flask (labeled Flask #3) from the top of the separatory funnel, taking care to not to transfer any water droplets. You add about 8 g of anhydrous sodium sulfate to this solution and give it to your instructor for evaluation and safe keeping. What does this solution contain? What is the purpose of using anhydrous sodium sulfate? What other compound/compounds could have been used in place of this salt?
7. You add concentrated hydrochloric acid drop-wise in the hood to Flask #1 until the contents are acidic to litmus and then cool the flask in an ice bath. What is the chemistry of the color change of the litmus paper in acid or base?
8. Now you isolate and weigh the compound in Flask #1. Weight of the crude compound (assume 70% yield): ____________.
9. Now go ahead and recrystallize from water this compound you have just isolated, and dry it by pressing it between several layers of filter paper, and then air-drying. Finally, you determine its melting point as accurately as possible.
Weight of recrystallized compound (suggest a reasonable figure):
Melting point of recrystallized compound (suggest a reasonable figure):
Would you expect the melting point to agree with that of a pure sample of this compound? Why?