Only the surface atoms in an adsorbent play an active role in adsorption. These atoms possess some residual force such as van der Waals forces and chemical forces. In the process of adsorption. Weak adsorbate is substituting by strong adsorbete. Activated charcoal used in the gas mask is already exposed to the atmospheric air, so gases and water vapours in air are adsorbed on its surface. When the mask is exposed to chlorine atmosphere, the gases are displaced by chlorine. In general, easily liquefiable gases such as `CO_(2),NH_(3),Cl_(2),` and `SO_(2)` are adsorbed to a greater extent than the elemental gases, e.g., `H_(2),N_(2),O_(2),` He, etc.
Which of the following gases will substitute `O_(2)` from adsorbed charcoal?
A. `Cl_(2)`
B. `N_(2)`
C. `CH_(4)`
D. `N_(2)`
