Percent Recovery Lab Report

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Percent Recovery was calculated by taking the total amount of grams collected and dividing it by the amount of grams initially started with and multiplying that number by 100.
Phthalic Acid: (.15g / .20g) * 100 = 75%
Benzoic Acid (Water): (.03g / .05g) * 100 = 60%
Benzoic Acid (Methanol): (035g / .05g) * 100 = 70%
Naphthalene: (.532g / 1g) * 100 = 53%
After the process of recrystallization was completed, the melting points and weights were taken for each solid. Some melting points recorded for the solids were very close to the values listed in the literature. However, others differed by sizeable margins from the values listed in the literature. The range observed for the melting point of naphthalene was 78-81°C. This coincides with
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The text suggested that the solvent be removed by evaporation via a hot water bath or filtration (Weldegrima 2016). A situation occurred during the lab where time had become a constraint and the hot water bath was being occupied by the naphthalene. The instructor advised that the sand bath be used to isolate the crystals from the solvent, or the crystals and liquid be poured on filter paper and hand dried. The sand bath was too hot and started to melt the solid. This led to the pouring of the liquid and crystals onto filter paper. This method left more room for error, as drying the crystals would be more tedious and it would be more difficult to remove all the crystals from the test tubes. The optimal percent recovery is a 100% for each solid. However, it is expected that less would be obtained. The percent recovery for the benzoic acid in both procedures and the phthalic acid were between 40%-25% less than the desired 100%. The low percent recovery can be attributed to the method previously mentioned, to separate the solvent from the crystals. When pouring the crystals and liquid onto the filter paper for the benzoic and phthalic acid, it could clearly be seen that there were many crystals still stuck to the inside of the tube. A spatula was used to recover as much of the crystals as possible, but not all of the crystals could be collected. This left many crystals still in the test tube which would have skewed the results for percent recovery, as they could not be weighed as well. The naphthalene was different, as it was not pure to begin with. A 1g solid mixture including an unknown amount of naphthalene was used. The lack of information on how much naphthalene was started with, makes it very cumbersome to determine the percent yield. However, .532g of naphthalene was recovered in total. There
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