(i) What is the role of activated charcoal in gas mask ?
(ii) How does chemisorption vary with temperature?

Explanation

(i) Activated charcoal is a good absorbent. Gas mask is usually used for breathing in coal mines to adsorb poisonous gas.
(ii) A negatively charged sol of hydrated ferric oxide is formed when ferric chloride is added to NaOH solution as follows:
`FeCl_(3)+2NaOHtoFe(OH)_(3)+3NaCl`
The negatively charged sol is obtained because of the preferential absorption of `OH^(-)` ions which form an electrical double layer.
(iii) The adsorption isobar of chemical adsorption shows that the extent of adsorption first increases and then decreases with the increase in temperature.