recrystallization of Benzoic acid

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Mabel M. Kimble

September 21, 2014

Chemistry 234

Recrystallization of Benzoic Acid


The recrystallization of Benzoic Acid was performed to fully master the ability to purify a solid compound. This form of purification technique is especially important in chemical identification, where the melting point of the compound is taken to confirm its purity. In order to perform recrystallization a solubility test much be completed. Four solvents (95% Ethanol, Petroleum Ether, Acetone and distilled water) were used to identify which one is an ideal solvent. An ideal solvent is insoluble in room temperature and soluble in hot solvent. 0.5mL of each solvent were added into four reaction tube with 25mg`of pure Benzoic acid. After careful observation, distilled water fit the requirement. During recrystallization, 0.5 grams of Benzoic acid were added into a 50mL flask with 10 mL distilled water. After performing this experiment, the first crop had a mass of .334

grams with a second crop of 0.0grams. The percent recovery yields 66.8%, which means that according to expected value of 70% this data confirms that the Benzoic is pure. Finally, the melting range was between 120 to 122 degrees which again confirms that the recrystallized Benzoic acid has been purified completely.


Recrystallization is a commonly used method of purifying solid compounds. Insoluble impurities get extracted from the compound by dissolving the mixture in hot solvent. The soluble impurities are dissolved in a high temperature environment and the solvent is cooled in room temperature while Benzoic acid crystallizes. The crystalized Benzoic acid is then placed in an ice bath to cool it further. The crystals are then filtered out using the vacuum filtration provided in lab. The filter paper is taken out and crystallized Benzoic Acid is dried out. Overall, the prediction for this experiment would be that...