For dilute solution, the van't Hoff equation is: ππV⇒M= VnRT=Mm2RT=πVm2RT Van't Hoff explained that when solutes are dissolved in a solvent they dissociate into ions. Since colligative properties depend only on the number of solute particles, the dissociation of solute molecules into ions results in an increase in the number of particles and hence affects the colligative properties.