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ABNORMAL MOLECULAR MASSES:, , When the molecular mass of a solute is calculated from the colligative, properties of solution (In which that solute has been dissolved), are sometimes, found to differ from experimentally obtained values. This value is called the, abnormal molar mass of that solute. The reason behind this is that some, solutes when dissolved in solutions get dissociated into ions or associate into, larger molecules., , Van’t Hoff Factor (i):, , Van’t Hoff factor is the measure of the effect of solute on various colligative, properties of solutions. It is given by —, , . Observed colligative property, i=, , , , Normal or theoritical colligative property, Normal Molar mass, *~ Observed molar mass, Actual number of particles, me Expected number of particles, , Van’t Hoff Factor for Associated Solutes and dissociated solutes can be, summarized in tabulated form as follows —, , , , Increases Increases Decreases, Decreases Decreases Increases, , If the solute neither undergoes association nor dissociation then the value of i, is 0., , Modified Mathematical Expressions of Colligative Properties in case of, Association or Dissociation of Solutes: