Question

In my liquid-liquid extraction experiment, I have to explain where the "rest" of my product is. we were given 1.000 gram to start with of one acid and one neutral compound and separated using the liquid liquid extraction. First we added NaOH into the flask and shook it and observe the separation of the two layers. Then I drained them into separate beakers and added HCL to the aqueous layer containing the acidic component and I evaporated the solvent off of my neutral compound. When I finished the experimen, the percent recovery of my acid was about 55 percent and the percent recovery of my neutral component was about 62 percent. Where did the rest of the product go? Or where could it have gone?

Answer 1

ANS.

As this is example of acid base work-up. As the compound 1 g compound contain acid and neutral compound, first you added NaOH aq, solution , the sodium hydroxide is strong base, it forms salts with acid and compound dissolved in aqueous layer.

Here you have to be careful regarding pH of the aq layer, it should be basic enough. so that all acid will come in aq layer,.

also you can extract one more time with NaOH solution.

then after seperation of layers, HCl added carefully to aq. slowly at lower temperature and pH should be acidic. so that compound extracts maximum from aq. layer.

For the recovery of neutral compound, initialy only after addition of NaOH solution, we can extract one or two time with organic solvent you used. and the pH should be basic not neutral.  

Most important the control on pH required.