`As_2 S_3` sol particles are negatively charged. The. sol can be precipitated by adding `BaCl_2`, solution. a How do you account for thè process? b. `AICl_3`, is more efficient than `BaCl_2`, in coagulating tbe sol. Justify. c. Throwing of electrical sand particles on clouds causè artificial rain. How will you describe this?

Explanation

a. .As_2 ~S_3. is a negatively charged colloid and on adding .Ba^2+. ions, the tons combine with charged colloidal particles and neutralise them. As the colloidal particles become free of charge, they unite together to form bigger particlés and finally get precipitated. .This process is known.as.coagulation.
b. The coagulation power of an electrolyte depénds on the valency of fon. ie., greater the valency, more is the coagulating power. Thus. .AlCl_3. is more efficient than .BaCl_2. in coagulating .As_2 ~S_3.,sol.
c. Artificial rain is formed by sprinkling electrically charged sand or silver iodide into c[ouds. Cloud is.a colloidal system and its charge gets rettralized. Thus, the colloidal water molecules coagulate to form rain.