Question

Identify the gas which is readily adsorbed by activated charcoal.
A. ${{\text{N}}_2}$
B. ${\text{S}}{{\text{O}}_2}$
C. ${{\text{H}}_2}$
D. ${{\text{O}}_2}$

Answer 1

For given adsorbent, a gas with high critical temperature is more likely to be adsorbed easily than a gas with low critical temperature. The gas readily absorbed is a major air pollutant.

Complete answer:
Adsorption is defined as the phenomenon of attracting and retaining the molecules of a substance on the surface of a liquid or a solid resulting in a higher concentration of molecules on the surface. The substance which is getting adsorbed is known as adsorbate and on which surface adsorption is taking place is known as adsorbent. Various factors affect adsorption, some are nature of adsorbate, nature of adsorbent, pressure, temperature, etc.
Talking about the nature of adsorbate, for a gas getting adsorb on a solid adsorbent; a gas which is easily liquefiable tends to get easily adsorbed. We can also say, a gas with high critical temperature tends to get easily adsorbed on the surface of solid adsorbent like charcoal. Critical temperature of some of the gases at NTP is given below:

Name of gas	Critical temperature in Kelvin
Hydrogen ${{\text{H}}_2}$	33
Nitrogen ${{\text{N}}_2}$	126
Methane ${\text{C}}{{\text{H}}_4}$	190
Carbon dioxide ${\text{C}}{{\text{O}}_2}$	304
Hydrochloric acid ${\text{HCl}}$	324
Ammonia ${\text{N}}{{\text{H}}_3}$	406
Sulphur dioxide ${\text{S}}{{\text{O}}_2}$	430

The order of critical temperature of these gases is: ${{\text{H}}_2} < {{\text{N}}_2} < {\text{C}}{{\text{H}}_4} < {\text{C}}{{\text{O}}_2} < {\text{HCl}} < {\text{N}}{{\text{H}}_3} < {\text{S}}{{\text{O}}_2}$ . Thereby w e can say that for same adsorbent like charcoal, the order of adsorption of these gases will be: ${{\text{H}}_2} < {{\text{N}}_2} < {\text{C}}{{\text{H}}_4} < {\text{C}}{{\text{O}}_2} < {\text{HCl}} < {\text{N}}{{\text{H}}_3} < {\text{S}}{{\text{O}}_2}$ .
Thus, the correct option is B.
Note:
Critical temperature of a gas is defined as the temperature at which or above which gas cannot be liquefied or we can it is defined as the maximum possible temperature at which gas can be liquefied by applying external pressure. It depends on the nature of gas.