Why do colligative properties of solution of a given concentration are found to give abnormal molecular weight of solute. Explain with the help of suitable examples.
The colligative properties have been found to give abnormal molecular masses due to the presence of fact about association or dissociation of solute molecules in solvent. To help this out Van’t Hoff factor was introduced which properly explained the fact. Solute undergoing association in the solution, Van’t Hoff factor is less than 1. Whereas, solute undergoing dissociation in the solution has Van’t Hoff factor more than 1. Example: KCl↔K++Cl−KCl↔K++Cl− Here, a molecule of KCl gives 2 ions which gives Van’t Hoff factor (i) as 2. This will reflect in the form of abnormal molecular mass calculations for certain conditions.
