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?

1).When a beam of light is passed through a colloidal solution,then it undergoes scattering.This scattering of light is an phenomenon which is known as Tyndall effect.Due to this the path of beam gets illuminated.
2).When NaCl is added to hydrated ferric oxide solution,then positively chraged colloidal particles of ferric oxide gets coagulated by oppositively chraged Cl- ions which are provided by NaCl.
3).On passing electric current thgrough a colloidal solution,then it is observed that colloidal particles start moving towards the oppositively charged electrode where they lose their charge and gets coagulated.