The Recrystallization of Benzoic Acid and the Physical Properties of Melting and Boiling Points (tot

Filtered using the hot gravity filtration in order to

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filtered using the hot gravity filtration in order to separate the insoluble impurities, meaning they have different phase or different mixing equilibrium, from that of the liquid. As the solution’s temperature is allowed to cool the benzoic acid becomes more saturated than already is and “drops out” thus the cause of the beginning form of the crystals. The solution is rapidly cooled by putting it on ice; this increases the rate of the benzoic acid becoming super saturated and “dropping out” of the solution. This is then the cause to pure benzoic acid crystal formation becoming more dense and abundant. Further explanation of this process was stated in the introduction.
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In the physical properties melting and boiling points experiment the distillation process was used to record and calculate the unknown C’s boiling point because when the substance began to vaporize a distillate was collected which then indicated when the recording of the temperature should begin. The recording temperature of the unknown C collected was that of 56 degrees Celsius. The temperature reached this degree at the last two mL of the 25 mL being collected. This concluding temperature corresponds to the standard boiling point of Acetone which is 56 degrees Celsius, allowing the conclusion that unknown substance C is that of Acetone to be formed. However, because the temperature of 56 degrees Celsius was not reached until the very end, it shows that impurities may have been contained within the solution, due to the fact that impurities will lower the boiling point of a substance. In the melting point part of the lab which included the pure and crude benzoic acid. The pure benzoic acid had an observed melting point range of 124.2 degrees Celsius to 125.4 degrees Celsius. The crude benzoic acid melting point consisted of a range from 125.1 degrees Celsius to 128.3 degrees Celsius. Impurities in a substance will lower and extend the melting point range of a substance (Proto). The crude benzoic acid was supposed to have a lower melting point and a greater range than that of the pure benzoic acid because the crude benzoic acid contains impurities. In this experiment the crude benzoic acid is 0.9 degrees Celsius higher than that of the pure. This could be due to human error such as not recording the temperature at the precise moment the crude benzoic acid melted, or it could be caused by the pure benzoic acid containing impurities or not being as pure as needed to correctly perform this experiment. The range of the crude benzoic acid is 3.2 degrees Celsius whereas the pure benzoic acid possesses a range of 1.2 degrees Celsius. This is an accurate calculation in the fact that the benzoic acid that contains the impurities has the greater melting point range.
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References: Proto, Justin. Class Lecture. Organic Chemistry Lab 1 Recitation. University of Pittsburgh, Pittsburgh, Pa. 13-20 September 2011. Huston, Ericka, and Chong Liu. Organic Chemistry 1 Laboratory Manual . Plymouth: Hayden McNeil, 2011. Print. Integrity Statement: I submit this lab report as an original document. I assert that all ideas and discussions of data contained herein is my own work, unless otherwise referenced.
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