Explain what is observed

(i) When a beam of light is passed through a colloidal sol

(ii) An electrolyte, NaCl is added to hydrated ferric oxide sol

(iii) Electric current is passed through a colloidal sol?

(i) In this case Tyndall effect is observed i.e. scattering of light by the colloidal particles takes place and the path of light become visible.

(ii) The coagulation takes place in this case positive charge particles of

Fe(OH) gets attached with Cl^-. And ppt. of FeCl is obtained.

(iii) In this case coagulation will take place. After passing electric current through colloidal solution particle will get attracted towards oppositely charged electrodes. and lose their charge and coagulate.