Chemical Engineering - Stoichiometry - Discussion
Discussion Forum : Stoichiometry - Section 8 (Q.No. 5)
5.
In physical adsorption, as compared to chemisorption, the
Discussion:
1 comments Page 1 of 1.
Pawan Kumar Sharma said:
2 years ago
Adsorption is the phenomenon of accumulation of large number of molecular species at the surface of a 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 the 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 van der Waal forces of attraction, the process is called Physical adsorption or Physisorption. Physical adsorption takes place with the formation of a multilayer of adsorbate on the adsorbent. It has a low enthalpy of adsorption, i.e., ΔHadsorption is 20−40 kJ/mol.
It takes place at a low temperature below the boiling point of the adsorbate. As the temperature increases in, the process of Physisorption decreases.
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 the formation of unilateral of adsorbate on the adsorbent. It has a high enthalpy of adsorption, i.e., ΔHadsorption is 200−400 kJ/mol. It can take place at all temperatures. With the increases in temperature, Chemisorption first increases and then decreases.
It is of following two types:
1. Physical Adsorption (Physisorption)
2. Chemical Adsorption (Chemisorption)
Adsorption processes take place by adsorbate getting adsorbed on the 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 van der Waal forces of attraction, the process is called Physical adsorption or Physisorption. Physical adsorption takes place with the formation of a multilayer of adsorbate on the adsorbent. It has a low enthalpy of adsorption, i.e., ΔHadsorption is 20−40 kJ/mol.
It takes place at a low temperature below the boiling point of the adsorbate. As the temperature increases in, the process of Physisorption decreases.
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 the formation of unilateral of adsorbate on the adsorbent. It has a high enthalpy of adsorption, i.e., ΔHadsorption is 200−400 kJ/mol. It can take place at all temperatures. With the increases in temperature, Chemisorption first increases and then decreases.
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