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Organic Chemistry Lab: Base Extraction 1. If you had a mixture that contained benzoic acid, 2-naphthol and napthalene how would the process of separating these three compounds differ from separating benzoic acid and naphthalene? 2. Compare the solvents used for extraction to a mixed solvent for recrystallization. a. Why would extraction not work if two miscible solvents were used? b. Why would crystallization not work if two immiscible solvents were used? 3. Compare and contrast the separation and purification of benzoic acid from: a. Malonic acid b. 1,4-dichlorobenzene. 4. What would happen if 0.5 M HCl was used to neutralize a NaOH solution containing benzoate ions? Consider the following when answering: a. Total Volume b. pH c. solubility of benzoate; solubility of benzoic acid 5. What would happen if the pH of an aqueous solution contaning benzoic acid was at 4.0 and not at 2.0?

Explanation / Answer

1. Use the aqueous sodium bicarbonate first to extract the benzoic acid. If you use sodium hydroxide, both phenol and benzoic acid will be extracted as both can react with hydroxide. If you use aqueous sodium bicarbonate, benzoic acid will be in aqueous layer as benzoate ion. Now label the first aqueous layer. Reapet the process again but use aqueous sodium hydroxide, phenol will be extracted as phenolate. Naphthalene will be remained in organic layer. For these two aqueous layers, add acid to acquire the additional proton these anions back to their respective conjugate acid.

2a. Extraction will not work if two miscible solvents were used beacuse of the Solubility level is maximum amount of a substance that will dissolve in a given amount of solvent at a specific temperature. There are two direct factors that affect solubility(temperature and pressure).

2b.Crystallization is used to purify a solid. A suitable solvent is readily dissolves in the solid (solute) when the solvent is hot but not when it is cold. due to this reason the crystallization will not work when two different immiscible solvents were used .

eg:-H2O(0-100*c )

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