A student runs a chromatograph of an unknown mixture, and after developing the s
ID: 1059021 • Letter: A
Question
A student runs a chromatograph of an unknown mixture, and after developing the spots with ninhydrin, get the following results. What are the R_f values for the two sports? report the values to the nearest 0.1 cm. In your experiment, the solvent moves 3 cm in about 5 minutes, but takes 60 minutes to move 7 cm. Why should you let your experiment run the full 60 minutes instead of stopping at 5 minutes? A particular experiment involving compounds "A" and "B" uses a solvent that is much Jess polar than the paper. If compound "A" is more polar than compound "B, " which of those two compounds will travel the farthest up the paper? Explain your reason(s).Explanation / Answer
Analysis of mixture by TLC
1. Rf value calculation
spot 1 = 0.8/1 = 0.8
spot 2 = 0.5/1 = 0.5
2. We should let the solvent run for full 60 minutes instead of 5 minutes so that the components of the mixture ets sufficient time to separate on the tlc plate.
3. For compound A and B.If compound A is more polar, it would move slower on the plate than less polar compound B. The Rf for compound A would be lower than the Rf for compound B. Less polar solvent would dissolve less polar compound first and move with the solvent up.
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