Question

Distinguish between true solution and colloidal solution of same colour.

Describe a method for distinguishing a colloidal solution from a true solution when the two have the same colour. 

Answer 1

Points	True solution	Colloidal solution
Appearance	A true solution appears transparent, even if it has colour (e.g. copper sulphate solution looks blue but clear).	A colloidal solution appears translucent or opaque, even if it has the same colour, due to scattering of light.
Particle size	The particles are very small (less than 1 nm) and cannot scatter light.	The particles are larger (1-1000 nm) and can scatter light, causing the Tyndall effect.
Visibility of Beam (Tyndall effect)	A true solution does not show the Tyndall effect; the path of light is not visible.	A colloidal solution shows the Tyndall effect; the path of light is visible.