Essay Sample on Separation of Benzoic Acid and Naphthalene Using One Base for Extraction

Introduction

The aim of the experiment is separate benzoic acid and naphthalene from their mixture using one base as the purification method of extraction. The phenomenon involves the application of base-acid chemistry where mixtures of compounds are separated into components which are pure. Apart from the extraction mechanism, the procedure of the experiment also involves the ideas of vacuum filtration, gravity filtration and as good as the mechanism of drying organic solutions. In this case, 0.0903 g of benzoic acid and 0.1007 of naphthalene is provided, the two compounds are mixed, and the process of separation begins, the mixture is placed in a centrifuge tube. To separate the mixture, first and foremost 3.5 ml of diethyl ether is added to the mixture. Diethyl ether is a solvent in which both naphthalene and benzoic acid are soluble in. 1 ml of sodium bicarbonate is then added in steps. Addition of this base is essential since due to the acidic nature of the benzoic acid, it reacts with sodium bicarbonate and not naphthalene since the latter is neutral. Significantly, the added sodium bicarbonate makes benzoic acid to participate in the base-acid reaction to form sodium benzoate, carbon dioxide, and water. The salt formed is soluble in water but does not dissolve in diethyl ether which is a complete opposite of naphthalene and benzoic acid which both are soluble in diethyl ether but not in water.

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It seems the experiment borrows the concept of recrystallization of acetanilide where solubility is the primary effector of the experiment. Though in this setup, the experiment incorporates the manipulation of base-acid properties of the compounds and changing one or more into new compounds to change its property in terms of solubility for instance benzoic acid is changed to benzoate which is soluble in water unlike before. (Kurnik, 93)

The time when sodium bicarbonate is added to the solution, the reaction that takes place makes the original solution to form layers, one at the bottom is the aqueous layer of sodium benzoate and water while the top layer is organic layer made of naphthalene and diethyl ether, the arrangement is connected to the density difference, water is much denser than diethyl ether. The aqueous bottom layer is the one removed and placed in the beaker. Another solution of sodium bicarbonate added makes the solution undergo the same procedure of reaction; the aqueous solution is separated as before and placed in the beaker. This is done with 1 ml three times being a total of 3 ml to make sure all the benzoic acid is converted to benzoate a salt which is soluble in the water released as a by-product.

Now for the retrieval of benzoic acid crystals, hydrochloric acid is added to the beaker containing the aqueous sodium benzoate, this procedure makes the sodium benzoate to be protonated thus benzoic acid crystals are formed in the water. The crystals are obtained through vacuum filtration where water is collected as filtrate and crystals of benzoic acid collected as residue. The crystals are smashed to dryness using a filter paper after which the recovered crystal is weighed for comparison with the original quantity that was used in the experiment.

Now, on the other hand, to recover the naphthalene in the centrifuge tube, some orderly steps are adhered to. In the centrifuge is the mixture of naphthalene contained in diethyl ether, a compound which is not soluble in water and for this reason, distilled water is added to the solution and mixed. The sole purpose of the distilled water is to dissolve any possible sodium benzoate that might still be present in the centrifuge tube. As usual, the bottom layer is aqueous sodium benzoate while the top layer is the organic solution of diethyl ether containing naphthalene. The bottom layer is discarded with the help of a pipette, and distilled water is added to the centrifuge tube, and the procedure is repeated four times to ensure the organic solution is free from the sodium benzoate. The organic solution is transferred to a clean test tube. 10% of anhydrous sodium sulfate is added to this solution. Anhydrous sodium sulfate is white and is mainly used as a drying agent. After the aqueous solution is extracted, the remaining organic solution has a percentage of water left in it. When sodium sulfate is added, sodium sulfate hydrate is formed, this is a solid which is filtered away, and so the remaining solution can be assumed to be free of water. (Jones, 204)

The beaker containing water at 2000C is used as a heat source for the organic solution now transferred to a new clean test tube. Before heating, the content plus the test tube is weighed and recorded and a boiling stick put inside it. When heating is done, the diethyl ether evaporates leaving behind the crystals of naphthalene. When the content is weighed again, weight contains no diethyl ether so that naphthalene is recovered.

The percentage of the naphthalene and benzoic acid recovered can then be calculated; this is the ratio of the recovered mass to the original mass used at the start of the experiment.

The reaction that occurs when anhydrous sodium sulfate is added to an organic solution containing diethyl ether and naphthalene is that the sodium ionizes in water and combine with the hydroxyl ions, and the result becomes a hydrated sodium sulfate, in the process as water is removed, the compound to which anhydrous sodium sulfate was added becomes dry.

The reactions shown above are explained in details in the earlier stages step by step that is, in the order in which they occur, how they are significant and mechanisms by which they occur. Therefore it is essential that one understands the mechanisms that occur in the experiment involving separation of compounds by the base-acid extraction approach and also the chemical equations that accompany them.

Works Cited

Jones, G. "The K noevenagel Condensation." Organic reactions 15 (2004): 204-599.

Kurnik, Ronald T., and Robert C. Reid. "Solubility of solid mixtures in supercritical fluids." Fluid Phase Equilibria 8.1 (1982): 93-105.