CHE_LAB5(Ext)

CHE_LAB5(Ext) - Separation and Isolation by Extraction...

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Separation and Isolation by Extraction Experiment 5
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Purpose Extraction is a classical process used to separate and isolate desired compounds. The following experiment is aimed towards a complete extraction and isolation of a mixture containing benzoic acid, 2-napthol, and 1,4-dimethoxybenzene. After separation, the respective compounds will be reacted, dried and tested for relative extraction success by melting point. Results and Discussions Flask 1 1.5 g of a benzoic acid, 2-napthol, and 1,4-dimethoxybenzene mixture was dissolved in 15 mL of diethyl ether and placed in a separatory funnel. 5g NaHCO 3 in 5 mL of water was added into the separatory funnel. The mixtures separated due to the differences in polarity. Water has a greater polarity than ether. The bubbling of the liquids and release of gas indicated that a reaction had occurred. C 6 H 5 COOH (aq) + NaHCO 3 (aq) NaC 6 H 5 COO (aq) + H 2 O (l) + CO 2 (g) Sodium bicarbonate (NaHCO 3 ) is a weak base and will react completely with the stronger acid (benzoic acid). The reaction yields water and a salt that is soluble in aqueous solution. Thus, the original benzoic acid exists now as the anion benzoate. Since diethyl ether has a lower density (0.7138g/cm 3 ) as compared to water, the aqueous layer will be on the bottom allowing separation. 1 In order to retain the original benzoic acid compound, a reaction with a strong acid (HCl) was undergone. Approximately 1.5 mL of HCl was added to the flask for an acidic pH indicating that C 6 H 5 COO - , the limiting reagent was used up. 1 Lide, D.R., ed. CRC Handbook of Chemistry and Physics, 87 th ed.; CRC Press: Boca Raton, FL, 2006; 3- 168.
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NaC 6 H 5 COO (aq) + HCl (aq) C 6 H 5 COOH (s) + NaCl (aq) Benzoic acid fell out of solution as a white precipitate. After removal by vacuum filtration, the mass was taken as 0.385g. Since the original mixture was a 1:1:1 ratio by
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This note was uploaded on 05/25/2008 for the course CHE 276 taught by Professor Totah during the Fall '07 term at Syracuse.

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CHE_LAB5(Ext) - Separation and Isolation by Extraction...

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