[xlovenuggetx]

Okay, so in this lab we took a propanoic acid solution and ethyl acetate and placed them together in a separatory funnel(20mL of each). The first time, we washed the aqueous solution once with 20mL of ethyl acetate. The second time we washed the acid solution twice with 10mL of ethyl acetate each time. We are supposed to see that two 10mL extractions are better (more efficient) than a single 20mL extraction. However my data doesn't seem to support this. The single 20mL extraction resulted in .27g of the acid remaining in water and .83g in the ethyl acetate. But the two 10mL extractions resulted in .44g of acid left in the water and .66g in the ethyl acetate.

Shouldn't we have observed more acid being removed in the two 10mL extraction than in the single 20mL extraction?

thoughts are much appreciated

[Nosterius]

Your procedure is not clear.

Is it an aqueous solution of propanoic acid, which you extract with ethyl acetate? Or is it an ethyl acetate solution of propanoic acid that you extract with water?

[xlovenuggetx]

an aqueous solution of propanoic acid being extracted with ethyl acetate.

[Nosterius]

Indeed, something must have gone wrong in your experiment.

How did you mesure the quantity of propanoic acid in water and ethyl acetate?

[fledarmus]

Did you shake your separatory funnel so that the two solvents were very thoroughly mixed before allowing them to separate? I apologize if this sounds like a dumb question, but when I taught this lab the first time, it never occurred to me to actually mention that, and a number of students thought they were just supposed to pour the ethyl acetate into the sep funnel and then drain the water out the bottom.

The two solvents have to be very thoroughly mixed for a sufficient time that the solutes can equilibrate between the two or your results will be badly off.