question_answer 23)

 Explain what is observed when (i) a beam of light is passed through a colloidal sol; (ii) an electrolyte i.e. NaCI is added to hydrated ferric oxide sol; (iii) electric current is passed through acolloidal sol?

Answer:

(i) When a beam of light is passed through a colloidal solution, placed in a dark room the beam of light is scattered by the colloidal particles and the path of the beam becomes visible. The phenomenon is called Tyndall effect. (ii) When NaCI is added to hydrated ferric oxide sot, the Cl– ions of NaCI neutralizes the positive charge on ferric hydroxide sol particles, and coagulation of sot occurs. (iii) When electric current is passed through a colloidal solution, the dispersed phase (or colloidal particles) move towards oppositely charged electrodes. On reaching the electrode, they lose their charge and get coagulated.