In regards to an extraction experiment involving Benzoic acid, 2- Naphthol, and

Question

In regards to an extraction experiment involving Benzoic acid, 2- Naphthol, and Fluorene

Describe and explain the possible effects on your results of the following experimental errors or variations. In each case, specify the component(s) whose percentage(s) would be too high or too low.

a) After adding 10% NaHCO3 to your mixture, you did not stir the mixture long enough.

b) During the 10% NaOH extraction, you failed to mix the aqueous and organic layers thoroughly.

c) You only neutralized the NaHCO3 solution to a pH of 7 instead of pH of 2

PLEASE TYPE ANSWERS, thank you!

Explanation / Answer

In the extraction experiment, the compounds which can be converted into ionic forms as a result of the addition of some chemical (say NaHCO3 here) will be soluble in the aqueous layer while the non-ionic forms will be soluble in the organic layer and the mixture can be separated. We need to note that Benzoic acid is a carboxylic acid, 2-Naphthol is alcohol (both are slightly acidic) whereas Fluorene is neutral in nature.

(a) The HCO3- in NaHCO3 will act as a base and will abstract the acidic proton from the carboxylic acid which will dissolve it in the aqueous layer allowing the separation of the acid from 2-Naphthol and Fluorene. The base cannot abstract the proton in case of 2-Naphthol here because it is a weak base and the proton in the alcohol is not acidic enough whereas the carboxylic acid proton is much more acidic relatively. This can be confirmed by pKa values of the two compounds. So, if the mixture is not stirred long enough, the complete acid will not be converted into ions and will not move into the aqueous layer thus, the percentage of acid in the mixture will be lowered but will not be zero and the other two concentrations will be same as before in the organic layer. It will be an inaccurate separation.

(b) NaOH is a strong base thus, will be able to dissolve both that is the acid and the alcohol in the aqueous layer. If the aqueous and organic layers are not mixed thoroughly, the percentage of the two will be lowered and inaccurate in the organic layer but will not be zero as it should be. The concentration of Fluorene will be same as before in the organic layer. It will be an inaccurate separation.

(c) If the NaHCO3 solution is neutralized to pH=7 and not pH=2, the NaHCO3 will still be protonated and will not be in the form of HCO3- thus, will not act as a base and abstract the proton from the acid. As a result of this, there will be no separation.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.