Which of the following colligative properties of colloidal solutions is used to determine the molecular mass?

Options

A. Relative lowering of vapor pressure
B. Elevation of boiling point
C. Depression of freezing point
D. Osmotic pressure

Answer

D

Explanation

Like true solution, colloidal sols show the colligative properties viz. relative lowering of vapour pressure, elevation in boiling point, depression in freezing point, and osmotic pressure. However, due to bigger aggregates, the number of particles in a colloidal solution is comparatively small as compared to a true solution. Hence, the values of the colligative properties observed experimentally are very small as compared to values shown by true solutions of same concentrations.
Only osmotic pressure measurements (which have relatively higher values) are used in determining the molecular mass of dispersed phase (solute).