1/ 2 Questions Please answer the following questions. Limited partial credit wil
ID: 1034787 • Letter: 1
Question
1/ 2 Questions Please answer the following questions. Limited partial credit will be given. 1. A student performs the following steps to isolate bipheny from a soid 1:1 micture of biphenyl and salicylic acid. a. Dissolve 2.0 grams of the mixture in 20 mL of ether b. Extract the ether layer 2-3 times with an aqueous solution of 5% sodium bicarbonate c. Add 2-3 spatula tips of sodium sulfate to the ether layer d. Extract the ether layer with a saturated aqueous solution of sodium chloride. e. Isolate the organic layer and evaporate the ether. The solid they collect at the end weighs 1.23 g and has a wide melting point range. the If the student expected to recover 1 gram of pure biphenyl, explain, based on procedural information given above, why this student did not see their expected results. Hint The order of steps in an extraction can be important. The mixture of benzoic acid, biphenyl, and benzocaine used in this experiment is soluble in acetone, a low boiling point organic solvent. Why would this be a poor choice of organic solvent for this experiment? Hint: think about what the requirements are for the solvents in an effective liquid-liquid extraction. 2. 3. Explain why saturated sodium chloride solution is used in liquid-liquid extractions Can the mixture of benzoic acid, biphenyl, and benzocaine still be separated from one another if 5% hydrochloric acid is added at the beginning of the extraction instead of 5% sodium bicarbonate? Exolain your answer 4.Explanation / Answer
1. Once both the compounds are dissolved in ether, sodium bicarbonate will make a salt with salicylic acid which will go to the aqueous layer. The biphenyl remains inthe ether which can be further washed with brine (aq. solution of NaCl) and then dried over Na2SO4 and evaporated to get the pure compound.
However, step C i.e., addition of sodium sulfate precedes extraction of ether layer with brine. It should after step D. hence, there may remain some aqueous part due to incomplete removal of aqueous layer from the ether layer which is causing the problem.
The correct procedure would follow: step a then step b then step d then step c and finally step e.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.