Explain the following observation:
a. A beam of light passing through a colloidal solution has a visible path.
Passing an electric currenet through a colloidal solution removes colloidal particles from it.
c. Ferric hydroxide sol coagulates on addition of potassium sulphate.

Explanation

This is due to scattering of light by the colloidal particles (called Tyndall effect).
b. This due to charge on the colloidal particles so that they migrate towards the oppositely charged electrode.
c. Ferric hydroxide is a positively charged sol and is coagulated by `SO_(4)^(2-)` ions produced by `K_(2)SO_(4)`