Explain what obsserved i.when a beam of light is passed through a colloidal sol. ii.an electrolyte,NaCl is added to hydrated ferri oxide sol. iii.electic current is passed through a colloidal sol.

Explanation

i. When a beam of light is passed through a colloidal sol kept in dark. the path of the light is illuminated by a biuish white light. This phenomenon of scattering of light by the colloidal particles in the sot is called tyndall effect.
ii. It gets coagulated. When an electrolyte like .NaCl. is added to .Fe(OH)_3. sol the positive charge on the colloidal particles is ręutralized by the CI-ions released by the electrolyte. Thus rendered neutral, the colloidal particles grow in size-and thus are.coagulated or precipitated. This phenomenon of rendering the charged colloidal particles neutral in the sol on the addition of an excess of electrolyte resulting in their precipitation is called coagulation or flocculatíon.
iii. When electric current is passed through some of the colloidal sols, the colloidal sol particles start moving towards the oppositely charge electrodes. This phenomenon of the movement of colloidal particles under an applied electric field towards the oppositely charged electrode is called cata"phoresis.or electrophoresis. If the particles accumulate near the negative electrode, the charge on the particles is positive. On the other hand, if the particles accamulate near the positive electrode, they have negative charge on them.