Question

Write a small introduction in words and a conclusion for this lab report

Experiment 9 Acid-Base Extraction Liquid-liquid extraction utilizes the contrast solubilities of solutes in two immiscible solvents the separation of a mixture. An extracting solvent can be reactive that changes the character of solute. Consider a mixture of organic acid, organic base, and neutral substance, for example, benzoic acid, aniline, biphenyl, nd phenol. They sodium benzoate. Sodium hydroxide changes phenol to sodium phenoxide. Hydrochloric acid changes aniline to anilinium chloride. are all soluble in diethyl ether but not water. Sodium carbonate changes benzoic acid to All these three salts are soluble in water but not ether, and the reactions are all reversible. The scheme of separation of these four compounds is outlined as follows: 1. Benzoic acid is extracted with aqueous sodium carbonate and recovered by acid neutralization. 2. Phenol is extracted with aqueous sodium hydroxide and recovered by acid neutralization. 3. Aniline is extracted with hydrochloric acid and recovered in liquid form by base neutralization. 4. Biphenyl remains in the final ether solution. 5. Collect each compound from the extracts and the remaining ether solution.

Answer 1

INTRODUCTION

Liquid-liquid extraction uses two unlike liquids, which are immiscible, to separate specific solutes whose solubility is changed when they react with one of the liquids. This essentially means that the product of the reaction of solute with one of the liquids is soluble in only one of the liquids and insoluble in the other liquid. The separating funnel is used to separate the two immiscible liquids after allowing for the time for reaction to occur. The compounds to be separated are in aqueous phase in the present case and are separated from it by acid or base neutralization.

CONCLUSION

1. Benzoic acid forms a soluble salt Sodium benzoate, which is soluble in aqueous phase. To extract benzoic acid from it, mineral acid is added to the aqueous phase after its separation from ether (organic phase). It turns back to benzoic acid and being insoluble, it forms precipitates.

2. Sodium phenoxide is again soluble in aqueous phase and after is separation from ether, concentrated mineral acid is added to it to the aqueous phase so that phenol ( a weaker acid than the mineral acid) is reformed. In the presence of concentrated mineral acid, phenoxide ion does not form in appreciable amounts and the equilibrium is largely towards phenol, which gets precipitated and can then be separated by filtration or decantation depending on the precipitates formed.

3. Similarly, aniline forms anilinium ion when HCl is added. Anilinium ion is soluble in aqueous phase and after its separation from organic phase, it can be extracted by neutralization with a strong base. Aniline, thus reformed, will be insoluble in aqueous medium and precipitate can be separated by filtration.

4. Biphenyl is a neutral compound and remains in the final ether solution. It cannot be separated by usual physical methods.