write equations (showing structures) for the reactions used in this experiment t

Question

write equations (showing structures) for the reactions used in this experiment to separate and recover benxzoic acid and nuphthalene. Verify the conclusion (drawn in Sec. I) that two extractions of A with 50-mL portions of ether yield 57.8 mg of A. whereas one extraction with 100 mL of ether yields only 53.5 mg of A. The solubility of suberic acid is 0.14 g/100 mL of water or 0.56 g/100 mLof ether. Calculate the volume of ether needed to remove 90% of the suberic acid from 100 mL of a saturated aqueous solution to a single extraction.

Explanation / Answer

5. Separation of benzoic acid and naphthalene

Add aqueous solution of NaHCO3 to the mixture. Benzoic acid reacts to form sodium salt, which goes in water. Naphthalene does not react and remains as it is. Separate water layer and acidify with conc. HCl to reprecipitate benzoic acid from water. The naphthlaene is obtained from original mixture from which benzoic acid is removed now.

Naphthalene(s) + C6H5COOH(s) + NaHCO3(aq) ----> C6H5COONa(aq) + Naphtlanene(s) + H2O(l) + CO2(g)

Separate,

C6H5COONa(aq) + HCl(aq) -----> C6H5COOH(s) + NaCl(aq)

6. we have,

In 100 ml of saturated solution, the amount of suberic acid present = 0.14 g

90% of this amount = 90 x 0.14/100 = 0.126 g

for 0.56 g of suberic acid, the volume of ether required = 100 ml

So, for 0.126 g suberic acid we would need = 0.126 x 100/0.56 = 22.5 ml ether

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