Surface Chemistry
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Class XII Chemistry Ch 5: Surface Chemistry Chapter Notes Top Concepts / Key learnings: 1. 2. 3. 4. 5. 6. Adsorption: The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. Adsorbate: The substance which is being adsorbed on the surface of another substance is called adsorbate. Adsorbent: The substance present in bulk, on the surface of which adsorption is taking place is called adsorbent. Desorption: The process of removing an adsorbed substance from a surface on which it is adsorbed is called desorption. Absorption: It is the phenomenon in which a substance is uniformly distributed all over the surface. Difference between adsorption and absorption: Absorption (i) It is the phenomenon in which a substance is uniformly distributed throughout the bulk of the solid. (ii) It is a bulk phenomenon. (iii) The concentration is uniform throughout the bulk of solid. Adsorption (i) The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. (ii) It is a surface phenomenon. (iii) The concentration of adsorbate increases only at the surface of the adsorbent.
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Sorption: When adsorption and absorption take place simultaneously, it is called sorption. Enthalpy or heat of adsorption: Adsorption generally occurs with release in energy, i.e., it is exothermic in nature. The enthalpy change for the adsorption of one mole of an adsorbate on the surface of adsorbent is called enthalpy or heat of adsorption.
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Types of adsorption:
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a. Physical adsorption or physisorption: If the adsorbate is held on a surface of adsorbent by weak van der Waals’ forces, the adsorption is called physical adsorption or physisorption. b. Chemical adsorption or chemisorption: If the forces holding the adsorbate are as strong as in chemical bonds, the adsorption process is
Class XII Chemistry Ch 5: Surface Chemistry Chapter Notes Top Concepts / Key learnings: 1. 2. 3. 4. 5. 6. Adsorption: The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. Adsorbate: The substance which is being adsorbed on the surface of another substance is called adsorbate. Adsorbent: The substance present in bulk, on the surface of which adsorption is taking place is called adsorbent. Desorption: The process of removing an adsorbed substance from a surface on which it is adsorbed is called desorption. Absorption: It is the phenomenon in which a substance is uniformly distributed all over the surface. Difference between adsorption and absorption: Absorption (i) It is the phenomenon in which a substance is uniformly distributed throughout the bulk of the solid. (ii) It is a bulk phenomenon. (iii) The concentration is uniform throughout the bulk of solid. Adsorption (i) The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption. (ii) It is a surface phenomenon. (iii) The concentration of adsorbate increases only at the surface of the adsorbent.
7. 8.
Sorption: When adsorption and absorption take place simultaneously, it is called sorption. Enthalpy or heat of adsorption: Adsorption generally occurs with release in energy, i.e., it is exothermic in nature. The enthalpy change for the adsorption of one mole of an adsorbate on the surface of adsorbent is called enthalpy or heat of adsorption.
9.
Types of adsorption:
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2
a. Physical adsorption or physisorption: If the adsorbate is held on a surface of adsorbent by weak van der Waals’ forces, the adsorption is called physical adsorption or physisorption. b. Chemical adsorption or chemisorption: If the forces holding the adsorbate are as strong as in chemical bonds, the adsorption process is