Organic Chemistry 1 2423 PDF

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Lab Summary as part of Organic Chemistry Lab instructed by Dr. Bernat Martinez...

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Isabella Manlapaz February 1, 2018

Organic Chemistry 1 2423- 540 In today’s lab, we performed two experiments. Our first experiment was determining the melting point of an unknown sample. In the following experiment, we carried out the recrystallization of impure benzoic acid. After the recrystallization experiment, I could determine based on my observations that benzoic acid is a pure substance because the melting point range between the initial and final temperatures was in the 1~2C range. The melting point is a physical property that describes the transition of a solid to a liquid. One of the techniques we used for the melting point in this lab was measuring the melting point of our unknown chemical in a capillary tube. When determining the melting point of the substance in the capillary tube, one will observe the solid in the tube until it begins to melt completely. The initial temperature is constant meaning that the melting point will never change no matter how much substance is placed in the capillary tube. After the experiment was conducted on the unknown chemical, the initial temperature was set at 132.4 C when I observed the first liquid formation. Once the substance was completely liquid, the final temperature was set at 137.0C. In the end, I was able to determine that based on the melting point, my unknown substances were consistent with either trans-cinnamic acid or benzoin. The determination of melting point range is also crucial in determining if a substance is pure or impure. In the following experiment we recrystallized impure benzoic acid. Recrystallization is a technique in which impurities are removed from a solid substance. This technique is highly dependent on the solubility of the target compound as well as other compounds present in the impure substance. Therefore, the goal of recrystallization is to have one compound completely

Isabella Manlapaz February 1, 2018 dissolved in a solvent while the other compound remains insoluble. As an impure substance, the melting point was determined to be 105.0 C- 116.7C. After determining the melting point of the benzoic acid, the impure substance was dissolved in deionized water and was later put into an ice bath. When the beaker containing the dissolved benzoic acid was placed into the ice bath, I began to observe the slow formation of crystals. If the temperature is very cold, the molecules begin to slow down and begin interacting with the solvent leading to the very slow formation of crystals. After the crystals were recovered, I determined the amount of benzoic acid recovered by measuring the percentage yield. The percentage yield is the mass of the pure sample divided by the mass of the initial sample. The amount recovered was 0.459 g of benzoic acid and when divided by the initial amount, 0.753 g, the percentage recovered was 61.2%. As soon as I calculated the percentage yield of the pure benzoic acid, I determined its melting point by placing it in a capillary tube and inserting the tube into the DigiMelt device to observe the melting point. The initial melting point of the pure benzoic acid was 120.3 C when the first drop of liquid appeared. The final melting point of the pure benzoic acid was 122.4 C. Based on the results, I was able to determine that benzoic acid is a pure substance because the melting point range of our substance was 2.1C. The reason this is a pure substance is because the melting point range is in the 1-2C range. In conclusion, I learned about how to determine the melting point of a substance, as well as the recrystallization of an impure substance, in this case, benzoic acid. I also learned in today’s lab that the melting point can be used to determine the purity of a substance and that recrystallization is a technique used to remove impurities from substances through purification. In addition, I also

Isabella Manlapaz February 1, 2018 learned about polar and non-polar compounds and that polarity and temperature are two factors in determining the purity of a substance. Overall, this experiment was a great lesson because I got to learn more about the melting point on a chemical level as well as the techniques used to measure this physical property....