Crystallization Laboratory, Lab Report Example

Purpose

The goal of the laboratory experiment was to conduct a purification of benzoic acid. The recrystallizing process had been performed in order to extract the impurities that had been in the sample. The quantity of benzoic acid that was extracted was melted had been a determining factor in identifying the unknown substance. It had been observed that in the evaluation of the distinct melting points, the pure and impure benzoic acid can be distinguished. The laboratory experiment had been conducted due to its attribute of providing significant knowledge regarding the chemical qualities and the reactivity manifested by a variety of compounds applied in everyday use.

Theory

As the desired compound had been extracted, there remained impurities in the precipitate. The impurities can be extracted by means of a procedure designated as recrystallization. The theory of recrystallization is founded upon three important concepts. The initial concept is that a solute always possesses greater solubility in heated solvents than in cold solvents. The second concept that is pertinent to the theory is that the molecules have solubility characteristics that are unique.

Finally, a developing crystal will only receive entities that are similar into its lattice. The third concept is directly correlated with the crystal lattice theory that delineates that crystal formation has an anti-entropic quality founded on the mathematical relationship of ?G = ?H- T ?S. Three stages of manifested solubility exist. These stages are known as the colliding stage, the disassociating stage and the solvation stage. Heat is aggregated to the system in order to elevate the potential of collision between the solute and initiate the dissociation. When all of the molecules have been liberated through the process of dissociation, solvation takes place (Mayo 85; Williamson & Masters 81).

Apparatus

Magnetic stirring bar, beaker, spatula, testing tube, transferring pipette, Buchner funnel, filtering flask, fluted filter paper, Erlenmeyer flask, heating plate and seamless funnel.

Procedure

One milliliter of ethyl acetate had been stirred in a testing tube containing benzoic acid. The solution had been swirled by means of agitation in order to verify if melting would occur in a cold aqueous solvent. The melting took place in water. One gram of charcoal was incrementally poured into a flask that had a volume of one hundred and twenty five milliliters. Distilled water had been gradually added until the charcoal experienced dissolution. Additional water had been aggregated by means of the transferring pipette. The solution had been stirred subsequent to the addition of heated water.

Approximately eight milliliters of water was aggregated in order to dissolve the charcoal. A supplemental Erlenmeyer flask had been aggregated to the hearting plate. The Erlenmeyer flask that had been aggregated to the heating plate had a seamless funnel that filtered the solute. Subsequent to the aggregation of the charcoal, the flask was placed on the counter in order to enable its refrigeration. As the flask become cooler, the crystalized liquid derived from the Erlenmeyer flask had been swirled and was placed into the filter. The process was conducted in order to deter its decantation. The flask had been rinsed with water three times and the solute had been placed into the Buchner funnel.

MSDS

Benzoic acid is an irritant that causes harm to the human metabolism by inhaling. Benzoic acid is also flammable. It is composed of flakes that are white and crystalline. (Chemical Land 21 1).

Ethyl Acetate is an irritant that is flammable. Repetitive exposure to the substance may cause the skin to crack and become dry. Eye shields should be applied in the handling of this substance (Sigma Aldrich 1).

Structures

A small amount of charcoal had been applied for the absorption of the molecules. The crystals of benzoic acid that had been retrieved had a flaky quality. The mass of benzoic acid that was retrieved was 2.23 g. The mass of the benzoic acid which had been crystalized was 1.84 g.

Tabulations

The amount of Benzoic acid that had been retrieved was determined by the following calculation:

1.84 g/ 2.43 g x 100 = 75.72%.

Melting Temperature laboratory

As the benzoic acid began melting, the process occurred rapidly. The crude benzoic acid manifested a wider melting temperature range

Melting Point Temperatures

Discussion

The objective of the process of recrystallization and the ascertaining of the melting point range had been the exploration of the approaches applied in order to acquire purified samples from the targeted compounds. Subsequent to the extraction, the objective became to recrystallize the benzoic acid and to calculate the percentage that was recovered. The outcome from the recovery demonstrate that approximately three quarters of the benzoic acid that had been recovered was pure. It can be deduced that the purified benzoic acid was accountable for the majority of the mass. There may have been some loss of the benzoic acid in the process of adding the solution.

In addition, the application of an ice bath reservoir could have had the outcome of decreasing the result regarding crystallization due to its attribute of being the last option for the recrystallization of the solute. It could also have been that the aggregation of the charcoal could have caused some of the solute to become absorbed. There could have been improvement in the experiment had there been more space available in the laboratory. There had been a variety of errors that had been committed due to the crowding of the material and the equipment. All in all the laboratory experiment was effective. The benzoic acid recrystallized and the values obtained were comparable to the empirical values.

Conclusion

The unknown substance was determined to be ethyl acetate. This determination had been made by its   point of ebullition and the capacity of being dissolved in water. In addition, the characteristics that were derived from the MSDs safety sheet confirmed many of the assumptions. The qualities of the substance cause it to be perceived as ethyl acetate.

References

Benzoic Acid MSDS. Chemical Land 21, 2015. Web. 26 October 2015.  http://chemicalland21.com/industrialchem/organic/benzoic%20acid.htm

Ethyl acetate MSDS. Sigma Aldrich, 2015. Web 26 October 2015 http://www.sigmaaldrich.com/catalog/product/sial/154857?land=en&region=US

Organic Chemistry Laboratory I and Laboratory II Second Edition pp. 335- 350.

Mayo, Dana W., Ronald W. Pike & David C. Forbes. Microscale Organic Laboratory: With Multistep and Multiscale Syntheses. Hoboken, NJ: John Wiley & Sons, Inc, 2011. Print.

Williamson, Kenneth & Katherine Masters. Macroscale and Microscale Experiments. Belmont, CA: Brooks/ Cole, 2011. Print.