chemistry

COLLIGATIVE PROPERTIES OF DILUTE SOLUTIONS

 A dilute solution is one in which the amount of the solute is very small in comparison to the amount of the solvent.The dilute solutions show more or less ideal behavior as the heat and volume changes, accompanying the mixing of solute and solvent, are negligible for all practical purposes.

Dilute solutions obey Raoult’s law.

 Dilute solutions containing non-volatile solute exhibit some special properties which depend only upon the number of solute particles present in the solution irrespective of their nature. These properties are termed as colligative properties. The colligative properties are:

 (i) Lowering in the vapour pressure,

 (ii) Elevation in the boiling point,

 (iii) Depression in the freezing point, and

 (iv) Osmotic pressure

Colligative properties are the properties of dilute solutions, that is why these are termed as colligative properties of dilute solutions. These properties are related to one another. Thus, if one is measured, the other can be calculated. The importance of these properties lies in the fact that they provide methods for the determination of molecular masses of dissolved solutes. The results are excellent if the following g three conditions are satisfied.

 (i) The solution should be very dilute.

 (ii) The solute should be non-volatile

 The solute does not dissociate or associate in solution