Post Lab Calculation Essay

Melting Point Data Table Compound Aspirin Caffeine Salicylamide Actual MP (ºC) 93 - 98 260 - 262 96 - 102 Expected MP (ºC) 135 236 140 Percent Error (%) ~30% ~12% ~30%

Prior to beginning the experiment, it is important to understand a few different concepts such as the distinguishing physical properties of a chemical substance and how these physical properties can be analyzed. Physical properties of a chemical substance include water solubility and melting point, both of which are used to pursue identification of the unknown component of Panacetin. Water solubility is a distinct physical feature of chemical substances that can lead to an increase or decrease in product recovered. For example, the water solubility of the two possible unknowns, acetanilide or phenacetin, are different in opposite temperature spectrums. Acetanilide’s cold water solubility is 0.54 grams/100 mL of water, whereas the substance’s boiling water solubility is 5.0 grams/100 mL of water.

During recrystallization, the solution was to be cooled to room temperature before placing it in an ice bath. Doing this allows enough time for the crystals to be formed because as the temperature decreases, the rate of crystallization slows down. If the solution was placed in the ice bath too quickly, then the cold would have blocked out the impurities and trapped them in the solution. The more impurities present, the lower the melting point so data would have been inaccurate. Also, if the melting point apparatus wasn’t set up correctly, the data would have been imprecise.

Acetylsalicylic acid has a molar mass of 180.16 g/mol. It has a melting point range of 134-136°C. Acetylsalicylic acid is toxic and an irritant.

No correction had to be made to the melting points because the standard melted in the range labeled on the bottle. The melted point observed is the correct melting point.

The melting point range of the unknown acid is most similar to the mixed range of the unknown acid and 2-chlorobenzoic acid, so the unknown acid is 2-chlorobenzoic acid.

Discussion: As seen in the melting point determination, the average melting point range of the product was 172.2-185.3ºC. The melting points of the possible products are listed as 101ºC for o-methoxybenzoic acid, 110ºC for m- methoxybenzoic acid, and 185ºC for p- methoxybenzoic acid. As the melting point of the sample

In order to discover the melting point range of Unknown 33A, a Digimelt was utilized. Melting point is the temperature at which a crystalline structure changes from solid to liquid. By adding thermal energy, the structure changed from solid to liquid. The thermal energy increased the kinetic energy, which then overcame the intermolecular attractive forces between the molecules. This increase in speed allowed the molecules to move more freely. By identifying the melting point range of Unknown 33A, it narrowed the possibilities of the unknown by ruling out the compounds with melting points greater than ± 20°C from Unknown 33A’s melting point range.

The temperature of the cooling bath must be adjust so that it is always about 3oC below the temperature of the contents.

1. During the first part of the experiment, it was concluded that given the information of the melting points of maleic acid and fumaric acid, the two unknown substances could be identified. In stating so, maleic acid had the melting point of 132.5 while fumaric acid had the melting point of 287. During the experiment, a pea-sized sample of each substance were collected and melted with a Bunsen burner.

The melting point that was observed for N-(4-butoxyphenyl)acetamide was 109.7˚C, and is lower than the literature value range of 131˚C. (Royal Society of Chemistry. 2018). This may be due to the presence of water and that impurities may be still present in the product that was formed. Solid substances that contain soluble impurities typically melts at a lower temperature than the pure compound (Kirsop. 2017). This is because the impurity disrupts the repeating pattern of forces that holds crystalline structure of the solid. A smaller amount of energy is required to melt the part of the solid surrounding the impurity, which supports that the compound that was produced was an impure compound.

The yellow color of the crystals determined that benzil was formed. The melting point of benzil is 94-96C (ChemSpider). However, the melting point achieved was 86C, as seen in Table 3. It was a narrow melting point range, thus indicating that benzil had impurities, such as solvent or reactant. Benzilic acid has a melting point of 148-152C (ChemSpider). As seen in Table 4, benzilic acid had a melting point of 145.4C. Benzilic acid also contains solvent or reactant impurities. The overall yield is computed by multiplying the pure, crude, and benzilic acid. The effect of low overall yield, hence indicates that the reaction was not successful.

Finally, the melting point of the aspirin was 110°C when it started melting and fully melted at

The three components of the unknown mixture were identified as Benzoic Acid, m-nitroaniline, and Naphthalene, as seen in Table 1. The melting point of the acidic component was 121.9℃-123.8℃ while the literature melting point of the suspected acid, Benzoic acid, is 121℃-122℃. The melting point of the basic component was 112.9℃-117.2℃ while the literature melting point for the suspected base m-nitroaniline was 111℃-114℃. The melting point for the neutral component was 77.9℃-82.8℃ while the literature melting point of the suspected compound Naphthalene is 79℃-82℃. The mixed melting point technique analytically confirmed the three identities of the components in the mixture because the melting point ranges for each component were extremely similar to the literature melting points of the suspected compounds.

The objectives of this lab are, as follows; to understand what occurs at the molecular level when a substance melts; to understand the primary purpose of melting point data; to demonstrate the technique for obtaining the melting point of an organic substance; and to explain the effect of impurities on the melting point of a substance. Through the experimentation of three substances, tetracosane, 1-tetradecanol and a mixture of the two, observations can be made in reference to melting point concerning polarity, molecular weight and purity of the substance. When comparing the two substances, it is evident that heavy molecule weight of tetracosane allowed