The correct statement(s) pertaining to the adsorption of a gas on a solid surface is(are):
(i) adsorption is always exothermic.
(ii) physisorption may transform into chemisorption at high temperature.
(iii) physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.
(iv) chemisorption is more exothermic than physisorption, however, it is very slow due to the higher energy of activation.
The correct statement(s) pertaining to the adsorption of a gas on a solid surface is(are):
(i) adsorption is always exothermic.
(iii) physisorption increases with increasing temperature but chemisorption decreases with increasing temperature.
(iv) chemisorption is more exothermic than physisorption, however, it is very slow due to the higher energy of activation.
The correct option is C (i), (ii) and (iv) only
Everytime a gas is adsorbed on a solid
surface, its movement is restricted leading to a decrease in the entropy of the
gas. The result is decreased in the surface energy of the adsorbent. Therefore,
adsorption is always exothermic.
Physical adsorption is an exothermic
process, it occurs more readily at lower temperatures and increases with
decreases in temperature.
Chemisorption occurs with formation of
unilayer of adsorbate on adsorbent. It has a high enthalpy of adsorption i.e. ΔHadsorption is 200−400 kJ/mol.
It can take place at all temperature. As temperature increases, Chemisorption
first increases and then decreases. It requires some energy of Activation and
is hence slow.
The correct option is A.
Everytime a gas is adsorbed on a solid surface, its movement is restricted leading to a decrease in the entropy of the gas. The result is decreased in the surface energy of the adsorbent. Therefore, adsorption is always exothermic.
Physical adsorption is an exothermic process, it occurs more readily at lower temperatures and increases with decreases in temperature.
Chemisorption occurs with formation of unilayer of adsorbate on adsorbent. It has a high enthalpy of adsorption i.e. ΔHadsorption is 200−400 kJ/mol. It can take place at all temperature. As temperature increases, Chemisorption first increases and then decreases. It requires some energy of Activation and is hence slow.
The correct option is A.
