Read the following passage and answer the questions.
Adsorption is surface phenomenon and its differ from absorption, Which occurs throughout the body of the substance which abosorbs. In physisorption, the attractive forces are mainly van der waals forces while in chemisorption actual bonding occuars between the particles of absorbent and absorbate. Generelly, easily liquifying gases are absorved more easily on the surface of a solid as compared to the gases which are liquified with difficulty. Adsorption increases with the increase in pressure and decreases as the temparature is increased.
Arrange the following gases in the decreasing order of the ease with which they are adsorbed on charcoal. `H_2`, `CH_4`, `CO_2` and `NH_3`