Which is not a Colligative property?

Hint: Colligative qualities are those of a solution that are determined by the ratio of the number of solute particles to the number of solvent particles in the solution, rather than the number of chemical species present.

Complete answer:
The number ratio can be linked to several concentration units for a solution, such as molarity, molality, normalcy (chemistry), and so on. For ideal solutions, the assumption that solution characteristics are independent of the type of solute particles is precise; for dilute actual solutions, it is imprecise. Colligative properties, in other words, are a collection of solution qualities that may be fairly approximated by assuming the solution is perfect.
Only attributes resulting from nonvolatile solute dissolution in a volatile liquid solvent are examined. They are essentially solvent characteristics that are altered when a solute is present. The solute particles displace some solvent molecules in the liquid phase, lowering the solvent concentration, therefore the colligative qualities are unaffected by the solute's type. The term colligative comes from the Latin word colligatus, which means "tied together." This means that all colligative qualities have one thing in common: they're all connected to the quantity of solute molecules compared to the number of solvent molecules, not to the type of the solute.
Relatively reduced vapour pressure (Raoult's law), elevation of boiling point, depression of freezing point, and osmotic pressure are all colligative qualities.
The colligative property, like boiling point, freezing point, osmotic pressure, and relative reduction of vapour pressure, is a characteristic of a solution that depends on the ratio of solute particles to solvent particles. However, several features of solutions, such as flavour, colour, solubility, and surface tension, are not interchangeable.
All colligative qualities are inversely proportional to solute molar mass for a particular solute-solvent mass ratio.

Note:
Measurement of colligative qualities for a dilute solution of a non-ionized solute like urea or glucose in water or another solvent can lead to relative molar mass estimations, both for tiny molecules and polymers that are difficult to study otherwise. Measurements of ionised solutes, on the other hand, can be used to estimate the proportion of dissociation taking place.