What determines the amount of time molecules spend in the phases
How soluble they are in solvent (Mobile phase)
How attracted they are to the paper (Stationary phase)
What happens to chemicals that have a greater solubilty in mobile phase
Substance which is more soluble in mobile phase will spend more time in that phase. This means it will move faster and therefore travel further than a less soluble chemical
Formula for Rf
Distance travelled by substance/Distance travelled by the solvent
