Given distance data on a TLC plate, calculate the Rf of the compound: origin to spot 48 mm; spot to solvent front 93 mm; origin to solvent front 141 mm.

Given distance data on a TLC plate, calculate the Rf of the compound: origin to spot 48 mm; spot to solvent front 93 mm; origin to solvent front 141 mm.

• A. 0.29
• B. 0.34
• C. 0.52
• D. 0.66

Answer: (B)

The key idea is that the retardation factor (Rf) is the ratio of how far the compound travels from the origin to how far the solvent front travels from the origin. Here, the spot is 48 mm from the origin and the solvent front is 141 mm from the origin, so Rf = 48 / 141 ≈ 0.340. Rounding to two decimals gives 0.34, which matches the correct option. Rf values are dimensionless and typically between 0 and 1 because a spot cannot move farther than the solvent front.

The key idea is that the retardation factor (Rf) is the ratio of how far the compound travels from the origin to how far the solvent front travels from the origin. Here, the spot is 48 mm from the origin and the solvent front is 141 mm from the origin, so Rf = 48 / 141 ≈ 0.340. Rounding to two decimals gives 0.34, which matches the correct option. Rf values are dimensionless and typically between 0 and 1 because a spot cannot move farther than the solvent front.