Use of Extraction to Isolate a Neutral Compound from a Mixture Containing an Acid Impurity.

Topics: Chemistry, Mixture, Chemical substance Pages: 4 (1235 words) Published: November 9, 2011
Introduction:
The purpose of this lab was to separate and purify a compound. This was achieved using techniques that allowed the extraction of the acid, the isolation of the neutral compound and the melting point classification of the neutral compound to test the purity of the sample.

Chemical Reactions:
HA+OH-A-+H2O

R-COOH+OH-R-COO-+H2O
Organic Acid
Insoluble in H2OConjugate base
Soluble in H2O

Procedure:
A 0.170g sample consisting of a mixture of 0.110g of an unknown neutral compound and 0.060g of benzoic acid was mixed with ether and shaken until all solids dissolved. NaOH was added, shaken, allowed to separate and the bottom layer removed and transferred to a test tube labeled “NaOH 1st extract”. NaOH was again added to the remaining original mixture, shaken, allowed to separate and the bottom aqueous layer was removed and transferred to a test tube labeled “NaOH 2nd extract”. HCl drops were added to both NaOH extracts until the mixtures turned acidic and a precipitate formed. NaCl was added to the original mixture, shaken and allowed to separate. The aqueous layer is removed and discarded. The remaining ether layer is transferred to a clean test tube and dried over granular anhydrous sodium sulfate. The dried ether solution is heated ina water bath until any remaining ether evaporated and only the unknown ingredient is left. The purity of the sample was verified by melting some of the crystallized sample and comparing the observed melting point range to the given melting point range of the listed unknown in the lab manual.

Calculations:
% Yield Recovery of sample= (end mass/starting mass) x 100

(0.050g / 0.170g) x 100 = 29.41%


Results:
Starting sample mass:0.170g Unknown Mixture composed of:
Neutral compound: 0.110g
Benzoic acid: 0.060g
Test tube mass:19.03g
Test tube and sample mass:19.08g
Final sample mass:00.05g
Percent yield recovery:
(0.050g / 0.170g) x 10029.41%
Melting...
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