Question

I'm practicing for my lab final and I came across a question I do not understand...

If a 0.092 g sample of a 1:1 mixture of acetylferrocene and ferrocene was separated by column chromatography, and the recovered fractions weighed 0.019 g (acetylferrocene) and 0.020 g (ferrocene), what was the percent recovery of acetylferrocene ?

a. 20.6%
b. 41.3%
c. 21.7%
d. 43.5%

I thought the answer was (a) because .019/.092 x 100 = 20.7, but it is saying the answer is (b). Can anyone please explain this? Thank you.

Answer 1

Here is how it was done.
0.092 was the total mass of both materials. It was a 1:1 mixture; therefore, each had a mass of 0.092/2 = 0.046 g.
percent recovery then for the one compound is [0.019/0.046]*100 = 41.3%,

I think the secret word is "recovery." If we wanted the percent in the original mixture, then a would be correct; however, when we say <i>recovery</i>, that means, "how much did we get out of what we put in" and this approach usually means we want some quantitative number for the effectiveness of the procedure.

Answer 2

Thanks so much for the help, I didn't even consider what you mentioned!

Again, I really appreciate it!