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andrade4 - EXPERIMENT 4: RECRYSTALLIZATION OF BENZOIC ACID...

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EXPERIMENT 4: RECRYSTALLIZATION OF BENZOIC ACID (FORMAL) Introduction: ___14____ / 15 pts Procedure: ____7___ / 7 pts Data and Results (6 points each) : ___20____ / 24 pts Table of Masses from Recrystallization (Part I) containing the initial mass of benzoic acid, the mass of the filter paper, the mass of the filter paper + benzoic acid, and the mass of the recovered benzoic acid. Table of Masses from Acid-Base Extraction (Part II) containing the initial mass of benzoic acid, the mass of the beaker, the mass of the beaker + the mass of benzoic acid, and the mass of recovered benzoic acid. Table of Melting Points - Melting points of crude and purified material along with literature value melting point for benzoic acid. Table of Percent Recovery Data Sample Calculations: ___3____ / 5 pts Percent recovery calculation. Discussion ____16___ / 20 pts Compare and contrast the two different purification procedures used in this experiment. Compare the percent recovery of benzoic acid obtained from the two different methods used in this experiment and discuss your findings. Compare the melting point obtained from your recrystallized benzoic acid to the melting point obtained from the impure benzoic acid sample you started with and to the melting point for benzoic acid reported in the literature. Discuss your findings with regards to the goals of this experiment. Observations from the experiment. Did results agree with what would be predicted? Is the discussion section cohesive and well written. 4 Questions: (6 points each) ___21____ / 24 pts Style (organization, neatness, proper formatting etc…) ____5___ / 5 pts Other Deductions (i.e., late lab report, incorrect formatting, etc…) - _______
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Score __86_____/ 100 pts
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The Extraction and Recrystallization of Benzoic Acid Francisco Andrade Jessica Booe 5/26/10 Wesley Storm CHEM 241L 402, Morehead Labs Room 301 Pledge
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Introduction: The objective of this experiment is to compare two different methods of purifying a crude sample of benzoic acid, acid-base extraction and recrystallization, by carrying out both methods and comparing the melting points of both purified samples with the melting point of the crude sample. Purification is meant to remove impurities present in the crude sample of benzoic acid, such as excess reagents, synthetic byproducts and other contaminants 1 . The process of recrystallization involves dissolving an impure solid in a hot solvent and then slowly regenerating a pure solid via crystallization. This process works because different compounds have different solubility characteristics in different solvents. Recrystallization begins with dissolving the impure solid in a hot solvent at a high temperature, which is followed by slowly cooling the solution, isolating the formed crystals by vacuum filtration, and ends with vacuum drying the crystals. The pure crystals reform without the impurities The acid-base extraction method utilizes the acid-base properties of benzoic acid. Even
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This document was uploaded on 11/04/2011 for the course CHEM 241 at UNC.

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andrade4 - EXPERIMENT 4: RECRYSTALLIZATION OF BENZOIC ACID...

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