Question

You are given a sample of several compounds to separate by paper chromatography. You draw a pencil line exactly 1.00 cm from the bottom of the paper, and place a spot of sample on it. You dry the sample, then develop it in a solvent. When the chromatogram is taken out of the solvent, the paper is wet up to 9.17 cm from the bottom of the sheet. The compound you are interested in shows up as a spot 7.57 cm from the bottom of the paper. Calculate the following:

a. How far did the compound move?
b. In the same time, how far did the solvent move?
c. What is the Rf factor for the compound?

Answer 1

a. 6.57 cm

b. 8.17 cm

c. 0.80

Step-by-step explanation:

a. The compound moved from where it was first placed, to a spot 7.57 cm from the bottom of the paper, in other words:

• 7.57 cm - 1.00 cm = 6.57 cm

b. A similar method is made for the solvent:

• 9.17 cm - 1.00 cm = 8.17 cm

c. The Rf of the factor is equal to the distance that the compound moved divided by the distance the solvent moved:

• 6.57 cm / 8.17 cm = 0.80