Question

Explain what is observed

When a beam of light is passed through a colloidal sol ?

An electrolyte, NaCl is added to hydrated ferric oxide sol ?

Electric current is passed through a colloidal sol ?

Answer 1

When a beam of light is passed through a colloidal sol., scattering of light takes place and the path of light becomes visible. (Tyndall effect)

When an electrolyte, NaCl is added to hydrated ferric oxide sol, charge on ferric hydroxide particles (+ve) is neutralised by -ve charge of $C{l}^{-}$ ions. Thus, coagulation takes place.

When electric current is passed through a colloidal sol., the colloidal particles move towards the oppositely charged electrode and the phenomenon is called electrophoresis.