Recrystallization of Acetanilide

May 29, 2018 | Author: maggumsx | Category: Filtration, Applied And Interdisciplinary Physics, Phases Of Matter, Physical Chemistry, Chemistry
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Maggie Xing | mx11 | 9/11/13 | Chem 201L-411 | Recrystallization of AcetanilideIn this experiment, we recrystallized acetanilide by saturating crude acetanilide with boiling water in an Erlenmeyer flask. Then, the solution in the Erlenmeyer flask was cooled and acetanilide crystals formed. These crystals were transferred to a filter paper for vacuum filtration to remove the liquid and the impurities dissolved in the liquid. The crystals were weighed to determine percent recovery. Then, a crude sample and a pure sample were each packed into capillary tubes for the determination of their respective melting points. In the end, our recrystallized Acetanilide looked like the literature description in that it was in the form of small, opaque, white crystals, but it also had little brown specks in the crystals. These were due to the brown impurities that had sunk to the bottom of the Erlenmeyer flask during the addition of boiling water and had been enclosed in the crystal during recrystallization. In reality, our recrystallization removed little of the impurities; most of the impurities bonded together in little brown pellets at the bottom of the Erlenmeyer flask, while the rest rose to the surface of the water and formed a small ring of brown matter on the inside of the flask. The impurities at the bottom simply got stuck in the recrystallized Acetanilide. Our melting point range for the crude and the pure had similar gaps, 5.8 and 6.6 degrees Celsius respectively. The crude range, 112.7-118.5 degrees Celsius, and the pure range, 109.5-115.7 degrees Celsius, showed a shift of about 3 degrees Celsius downwards, from crude to pure. Impurities are supposed to lower and broaden the melting range; the opposite happened with our experiment. The literature melting range according to www.sigmaaldrich.com is 113-115 degrees Celsius. A possible explanation for the lowering and broadening of our melting range is that when we packed our crude and pure samples into the capillary tubes for melting point determination, the crude tube had .5 mm to 1 mm more inside it that the more loosely packed pure sample. This Ideally. Our percent recovery was 63.Maggie Xing | mx11 | 9/11/13 | Chem 201L-411 | Recrystallization of Acetanilide may affect melting point. and were difficult to scrape off.sigmaaldrich. and from the filter paper to the weighing boat.com/catalog/product/aldrich/397229?lang=en®ion=US>. But this was not the case. we would have packed the crude and pure samples identically..p. Ideally. Literature source: . . After recrystallization. and the brown impurities would have dissolved into the hot water and been removed with the water by vacuum filtration. and we wanted to avoid scraping those. A good percent recovery is 80%. as the other group that was using the same melting apparatus had packed much less of their pure sample into their tube. it is not possible to get all of the crystals off of the filter paper after vacuum filtration. <http://www. Similarly. Web. The brown ring of impurities was also stuck on the side. crystals had formed on the inside of the Erlenmeyer flask. 4 Sep 2013. and it started melting at a much lower temperature than our pure sample. N. so our sample was not very pure and was far from completely recovered. we would be able to scrape all of the crystals off of the Erlenmeyer flask and filter paper.8%. Much of the crystals were left in the flask due to the difficult angle and the reluctance to accidentally scrape out impurities. so the process became more difficult. The mass lost over the experiment must have been lost during transferring from the Erlenmeyer flask to the filter paper.


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