Average number of moles:
This fraction is equivalent to average number of moles of a solute in the mobile phase at any instant divided by the total number of moles of the solute in the column.
v = u × Moles of the solute in mobile phase/ Total moles in the column
A number of moles of the solute in the mobile and stationary phases is the product of their concentration and respective volumes
v = u × C M VM/(C M VM + C S VS)
where, C and V denote the concentration and volume, correspondingly
v = u × 1/(1 + C S VS /C M VM)
We know that K = C S/C M
Thus, we have a relation between solute migration and distribution constant
v = u × 1/(1 + KVS /VM)