Question

Thin layer chromatography was performed on an unknown substance. The substance separated into two spots: A AND B. Spot A travelled 3.85 cm and Spot B travelled 5.98cm. The colvent travelled 7.54 cm.

1.) Which of the two components (A or B) was more attracted to the stationary phase? Explain

2.) Calculate the Rf and of A and B. (show work)

3.) An analysis on an unknown showed one spot with an Rf of 0.52. Which component was the unknown, A or B? Explain.

Answer 1

1.

Spot A traveled 3.85 cm.

Spot B traveled 5.98 cm.

The spot that traveled the lower distance among the two spots was more attracted to the stationary phase. Hence, the component A was more attracted to the stationary phase.

2.

Distance that solvent front traveled = 7.54 cm

R_f of A = distance traveled by spot A/distance traveled by solvent

            = 3.85 cm / 7.54 cm

            = 0.51

R_f of B = distance traveled by spot B/distance traveled by solvent

            = 5.98 cm / 7.54 cm

            = 0.79

3.

Analysis on an unknown showed one spot with an R_f of 0.52 which matches with the R_f (0.51) of component A. Hence, the component A was the unknown.