Snape grows tired of these conceptual questions and thinks it's time for a problem. what is the retention factor if the distance travelled by the solvent front is 2.00 cm, and the distance travelled by the ion is 0.40 cm?

The Retention factor (rf) value is = 0.2

Explanation:

Retention factor (Rf) is factor used substances that could be separated using Chromatography. Retention factor determines how fast the component can move on the chromatogram (stationary phase) after elution. Elution occurs when mobile phase (solvent) moves across the stationary phase when the solute has been spotted on the origin. Retention factor (Rf) ranges from value between 0 and  1. The closer the value to 1, the faster it can move upon elution. Rf can be calculated. Rf value = distance moved by the solute / distance moved by the solvent

             = 0.40cm / 2.00cm

             = 0.2