Q14 of 36 Page 1

(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 charcoal is basically used in gas masks to prevent coal miners from suffocation from ashes and poisonous gases. The toxic gases get absorbed over the surface of activated charcoal and bind with weak forces like van-der-waal forces. The larger and heavy particles are unable to enter through the mask and the person doesn’t inhale poisonous gases and ash.


(ii) Colloidal particles adsorb charges or ions which are in excess and common to the colloidal particle. Development of charge on sol particle is due to the formulation of an electrical double layer. When FeCl3 is added in NaOH, then due to excess of OH- ions n the dispersion medium, the sol attains overall negative charge. Sol representation will be Fe2O3xH2O/OH-.


(iii) Chemisorption process involves formation of chemical bonds within adsorbate and adsorbent and therefore depends on temperature conditions. With the increase in temperature, chemisorption increases up to a certain limit and then starts decreasing.


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