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CHM142 experiment2 - SchoolofChEChm RottenCarbonoids...

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Romero, Von Joby M. Experiment No. 2:  RECRYSTALLIZATION ABSTRACT Recrystallization is a common method of purifying an organic compound through  the application of the principles of solubility. The experiment is intended first to  gain understanding regarding organic compound’s solubility given the condition  such as temperature as well as the type of solvent used. Solvents used were  water, ethanol, benzene and ethyl alcohol. These were analyzed to identify the  solvent   appropriate   for   recrystallization   for   the   given   organic   compounds.  Afterwards,   application   of   recrystallization   was   made.   Crude   acetanilide  dissolved in a solvent was introduced in a heating water bath. Adsorption of small  impurities was done before filtration, to remove all unwanted impurities. The  solution was cooled slowly in an ice bath as crystals form out. As the compound  crystallizes   from   the   solution,   molecules   of   other   compounds   (impurities)  dissolved in solution are excluded from growing crystal lattice, yielding pure  acetanilide. To test if the substance recovered was purified correctly, its melting  point was determined using the method applied in the first experiment. Aside  Page 1 School of ChE-Chm Rotten Carbonoids Chm142L     B11 Group No. 11 07/30/2010
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from this, the amount of pure sample was compared to the original weight. Based  on the results, crude acetanilide was purified. I. INTRODUCTION Possessing   an   extensive  understanding regarding solubility of  organic compounds aids us greatly  in   recrystallization   process.   Solid  organic   compounds   at   room  temperature are typically purified by  crystallization.   This   process   is   the  deposition of crystals from a solution.  In   crystal   formation,   the   molecules  have a great tendency to join itself to  a growing lattice of a molecule of the  same structure. Lattice is a fixed and  rigid   arrangement   of   atoms,  molecules or ions. Recrystallization  is   a   method   in   which   two  crystallization processes was carried  out.   It   is   referred   to   the   second  crystallization.   It   depends   on   the  difference of solubility of a substance  in a hot and in a cold solvent.  Recrystallizing   solvent   is   a   solvent  that   shows   the   desired   solubility  behavior   for   the   substance   to   be  crystallized.   Identifying   the   ideal  recrystallizing solvent of a compound  is   necessary   to   purify   the   organic  compound. Trial-and-error method is  commonly done when the compound  to   be   purified   is   unknown.   In  choosing the recrystallizing solvent, 
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