Lab 2 report edit.docx - Lab 2 Solubility and Extraction CHEM 345 Section 4 Abstract The acid-base properties of benzoic acid were demonstrated using

Lab 2 report edit.docx - Lab 2 Solubility and Extraction...

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Lab 2: Solubility and Extraction CHEM 345 Section 4 9/15/19 Abstract: The acid-base properties of benzoic acid were demonstrated using the technique of liquid-liquid extraction. Solid benzoic acid was dissolved in diethyl ether and then sequentially extracted with 3 M HCl and 3 M NaOH solutions, resulting in an ether fraction, an acidic fraction, and an alkaline fraction. Evaporation of the ether fraction gave nothing. Treatment of the acid extract with base to ~ pH 10 gave a clear solution. Treatment of the alkaline fraction with acid to ~ pH 2 gave solid benzoic acid. Introduction/Purpose: Organic acids and bases, to the extent that they are relatively non-polar, maybe sparingly soluble in polar water. waters dielectric constant is 78.5 (1). Benzoic acid has a solubility in water of 2g/100mL water, or 100% (1). In contrast, diethyl ether is relatively non- polar with dielectric constant of 4.3 (1). Benzoic acid, therefore, is expected to be more soluble in ether than in water. If dielectric constants are quite different, the liquid's maybe immiscible (mostly insoluble in each other). Benzoic acid, however, can be chemically manipulated. Since it is an acid, it will react with a base like NaOH according to the following balanced reaction: C 7 H 6 O 2 + NaOH → C 7 H 5 O 2 Na + H 2 O A product of this reaction, sodium benzoate, is ionic and therefore quite polar, and much more soluble in water than benzoic acid. Thus, benzoic acid dissolved in ether and treated with an NaOH solution will, upon mixing, allow the benzoic acid to move into the aqueous phase in the form of sodium benzoate. Since the aqueous phase is not soluble in ether, they can be separated.
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