Choose the correct statement(s) pertaining to the adsorption of a gas on a solid surface.
Choose the correct statement(s) pertaining to the adsorption of a gas on a solid surface.
The correct options are
A Adsorption is always exothermic.
D Chemisorption is more exothermic than physisorption, however, it is very slow due to higher energy of activation.
Adsorption is the phenomenon of accumulation of large number of molecular species at the surface of liquid or solid phase in comparison to the bulk.
It is of following two types:
1. Physical Adsorption (Physisorption)
2. Chemical Adsorption (Chemisorption)
Adsorption processes take place by adsorbate getting adsorbed on adsorbent.Forces of attraction exist between adsorbate and adsorbent and due to these forces of attraction, heat energy is released. So, all adsorptions are exothermic processes.
1. Physical Adsorption:
When the force of attraction existing between adsorbate and adsorbent are weak Vanderwaal forces of attraction, the process is called Physical Adsorption or Physisorption. Physical Adsorption takes place with formation of multilayer of adsorbate on adsorbent. It has low enthalpy of adsorption i.e. ΔHadsorption is 20−40 kJ/mol.
It takes place at low temperature below boiling point of adsorbate.As the temperature increases in, process of Physisorption decreases.
It does not require any energy of Activation and is generally instantaneous.
2.Chemical Adsorption:
When the force of attraction existing between adsorbate and adsorbent are chemical forces of attraction or chemical bond, the process is called Chemical Adsorption or Chemisorption. Chemisorption takes place with formation of unilayer of adsorbate on adsorbent. It has high enthalpy of adsorption i.e. ΔHadsorption is 200−400 kJ/mol.
It can take place at all temperature. With the increases in temperature, Chemisorption first increases and then decreases.
It requires some energy of Activation and is hence slow.
Hence Answer is Option AandD
A Adsorption is always exothermic.
D Chemisorption is more exothermic than physisorption, however, it is very slow due to higher energy of activation.
Adsorption is the phenomenon of accumulation of large number of molecular species at the surface of liquid or solid phase in comparison to the bulk.
It is of following two types:
1. Physical Adsorption (Physisorption)
2. Chemical Adsorption (Chemisorption)
Adsorption processes take place by adsorbate getting adsorbed on adsorbent.Forces of attraction exist between adsorbate and adsorbent and due to these forces of attraction, heat energy is released. So, all adsorptions are exothermic processes.
1. Physical Adsorption:
When the force of attraction existing between adsorbate and adsorbent are weak Vanderwaal forces of attraction, the process is called Physical Adsorption or Physisorption. Physical Adsorption takes place with formation of multilayer of adsorbate on adsorbent. It has low enthalpy of adsorption i.e. ΔHadsorption is 20−40 kJ/mol.
It takes place at low temperature below boiling point of adsorbate.As the temperature increases in, process of Physisorption decreases.
It does not require any energy of Activation and is generally instantaneous.
2.Chemical Adsorption:
When the force of attraction existing between adsorbate and adsorbent are chemical forces of attraction or chemical bond, the process is called Chemical Adsorption or Chemisorption. Chemisorption takes place with formation of unilayer of adsorbate on adsorbent. It has high enthalpy of adsorption i.e. ΔHadsorption is 200−400 kJ/mol.
It can take place at all temperature. With the increases in temperature, Chemisorption first increases and then decreases.
It requires some energy of Activation and is hence slow.
Hence Answer is Option AandD
