(i) What is the role of activated charcoal in gas mask?
(ii) A colloidal sol is prepared by the given method in figure. What is the charge on hydrated ferric oxide colloidal particles formed in the test tube? How is the sol represented?

(iii) How does chemisorption vary with temperature?

(i) Activated carbon or activated charcoal is an extremely porous carbon that has a very large surface area available for adsorption or chemical reactions. It is the most widely used adsorbent for preparing gas masks to selectively adsorb toxic gases.  

(ii) The coagulation will take place when FeCl₃ is added to NaOH solution. The Fe(OH)₃ gets coagulated by the oppositely charged particle Cl⁻. 

(iii) Adsorption is always accompanied by evolution of heat, so according to Le Chatelier’s principle, the magnitude of adsorption should increase with a decrease in temperature. In chemisorption since it requires some activation energy, the magnitude of adsorption increases initially and then decreases with an increase in temperature.