Question

Hi, I am currently working on "Thin Layer Chromatography" lab. I know retention formular is Rf= (Distance moved by compound) / (Distance moved by the mobile phase). listed below are my questions

1.What is the formula for the retention factor (Rf) for which a compound travels?

options are Rf=x-y Rf=x+y Rf=x/y Rf= x EE y

a. Where X is distance from the compound spot to the solvent front

distance from the bottom of the plate the the compound spot

distance from the origin to the solvent front

distance from the bottom to the top of the plate

distance from the bottom of the plate to the solvent front

distance from the origin to the top of the plate

distance from the origin to the origin to the compound spot

distance from the compound spot to the top of the plate

b.And Y is distance from the compound spot to the solvent front

distance from the bottom of the plate the the compound spot

distance from the origin to the solvent front

distance from the bottom to the top of the plate

distance from the bottom of the plate to the solvent front

distance from the origin to the top of the plate

distance from the origin to the origin to the compound spot

distance from the compound spot to the top of the plate

2. Which is the most polar of each solvent pair?

a. Toluent or Ethyl Acetate?

b. Methanol or DCM (dichloromethane)?

c. Benzene or Phenol?

d. Benzoid or Cyclohexane?

Answer 1

1.

Rf = (Distance moved by compound) / (Distance moved by the mobile phase)

Rf = x/y

x = distance from the origin to the origin to the compound spot
[distance from the origin (where the compound spoted) to the new position of the compound in TLC]

y = distance from the origin to the solvent front

This is based on defination of Rf value

2.

Answer is (b) Methanol or DCM (dichloromethane)

Both Methanol and DCM are polar solvents.

In option (a) Toluent, (c) Benzene and (d) Cyclohexane; one is non-polar solvent.