Flashcards for JEE Chemistry - Surface Chemistry Class 12

 Page 1


Surface Chemistry
Flash cards
Page 2


Surface Chemistry
Flash cards
Introduction (Continued)
It has been known that the surface of a liquid is in a state of strain or unsaturation 
due to the unbalanced or residual forces which act along the surface of a liquid. 
Similar to it, the surface of a solid may also have residual forces or valencies. Thus, the 
surface of a solid has a tendency to attract and to retain molecules of other species (gas 
or liquids) with which such surfaces come in contact. This phenomenon of surfaces is 
termed as adsorption.
As the molecules remain only at the surface, and do not go deeper into the bulk of 
the solid, the concentration of adsorbed gas or liquid is more at the surface than in the 
bulk. Hence this discussion may follow up by the definition of adsorption.
"Adsorption is a technical term coined to denote the taking up (Latin, surbere, to 
suck up) of gas, vapour, liquid by a surface or interface".
Page 3


Surface Chemistry
Flash cards
Introduction (Continued)
It has been known that the surface of a liquid is in a state of strain or unsaturation 
due to the unbalanced or residual forces which act along the surface of a liquid. 
Similar to it, the surface of a solid may also have residual forces or valencies. Thus, the 
surface of a solid has a tendency to attract and to retain molecules of other species (gas 
or liquids) with which such surfaces come in contact. This phenomenon of surfaces is 
termed as adsorption.
As the molecules remain only at the surface, and do not go deeper into the bulk of 
the solid, the concentration of adsorbed gas or liquid is more at the surface than in the 
bulk. Hence this discussion may follow up by the definition of adsorption.
"Adsorption is a technical term coined to denote the taking up (Latin, surbere, to 
suck up) of gas, vapour, liquid by a surface or interface".
Introduction (Continued)
Differences between Adsorption, Absorption and Sorption. Adsorption is a surface 
phenomenon whereas absorption is a bulk phenomenon in which the substance 
assimilated is uniformly distributed throughout the body of a solid or liquid to form a 
solution or a compound.The phenomenon of adsorption and absorption are 
illustrated in figure.
Adsorption should be distinguished carefully from absorption.
Page 4


Surface Chemistry
Flash cards
Introduction (Continued)
It has been known that the surface of a liquid is in a state of strain or unsaturation 
due to the unbalanced or residual forces which act along the surface of a liquid. 
Similar to it, the surface of a solid may also have residual forces or valencies. Thus, the 
surface of a solid has a tendency to attract and to retain molecules of other species (gas 
or liquids) with which such surfaces come in contact. This phenomenon of surfaces is 
termed as adsorption.
As the molecules remain only at the surface, and do not go deeper into the bulk of 
the solid, the concentration of adsorbed gas or liquid is more at the surface than in the 
bulk. Hence this discussion may follow up by the definition of adsorption.
"Adsorption is a technical term coined to denote the taking up (Latin, surbere, to 
suck up) of gas, vapour, liquid by a surface or interface".
Introduction (Continued)
Differences between Adsorption, Absorption and Sorption. Adsorption is a surface 
phenomenon whereas absorption is a bulk phenomenon in which the substance 
assimilated is uniformly distributed throughout the body of a solid or liquid to form a 
solution or a compound.The phenomenon of adsorption and absorption are 
illustrated in figure.
Adsorption should be distinguished carefully from absorption.
Introduction (Continued)
(i) In absorption, the substance is distributed throughout the body of a solid or a 
liquid to form a solution or a compound. On the other hand, adsorption only takes 
place on the surface and not in the body of adsorbent. Thus, adsorption is a surface 
phenomenon, and absorption is a bulk phenomenon.
(ii) In absorption, the concentration of the adsorbed molecules is always found to be 
greater in the immediate vicinity of the surface (Adsorbent) than in the free phase 
(Adsorbate). On the contrary, absorption involves bulk penetration of the molecules 
into the structure of the solid or liquid by some process of diffusion.
(iii) In case of adsorption, the equilibrium is easily attained in a very short time 
whereas in absorption the equilibrium takes place slowly
Page 5


Surface Chemistry
Flash cards
Introduction (Continued)
It has been known that the surface of a liquid is in a state of strain or unsaturation 
due to the unbalanced or residual forces which act along the surface of a liquid. 
Similar to it, the surface of a solid may also have residual forces or valencies. Thus, the 
surface of a solid has a tendency to attract and to retain molecules of other species (gas 
or liquids) with which such surfaces come in contact. This phenomenon of surfaces is 
termed as adsorption.
As the molecules remain only at the surface, and do not go deeper into the bulk of 
the solid, the concentration of adsorbed gas or liquid is more at the surface than in the 
bulk. Hence this discussion may follow up by the definition of adsorption.
"Adsorption is a technical term coined to denote the taking up (Latin, surbere, to 
suck up) of gas, vapour, liquid by a surface or interface".
Introduction (Continued)
Differences between Adsorption, Absorption and Sorption. Adsorption is a surface 
phenomenon whereas absorption is a bulk phenomenon in which the substance 
assimilated is uniformly distributed throughout the body of a solid or liquid to form a 
solution or a compound.The phenomenon of adsorption and absorption are 
illustrated in figure.
Adsorption should be distinguished carefully from absorption.
Introduction (Continued)
(i) In absorption, the substance is distributed throughout the body of a solid or a 
liquid to form a solution or a compound. On the other hand, adsorption only takes 
place on the surface and not in the body of adsorbent. Thus, adsorption is a surface 
phenomenon, and absorption is a bulk phenomenon.
(ii) In absorption, the concentration of the adsorbed molecules is always found to be 
greater in the immediate vicinity of the surface (Adsorbent) than in the free phase 
(Adsorbate). On the contrary, absorption involves bulk penetration of the molecules 
into the structure of the solid or liquid by some process of diffusion.
(iii) In case of adsorption, the equilibrium is easily attained in a very short time 
whereas in absorption the equilibrium takes place slowly
Introduction (Continued)
(iv) Typical isotherms for adsorption and absorption are shown in figure.
Typical isotherms for adsorption,and absorption respectively
If x/m is plotted against p or c, the graph should be a straight line in adsorption and a 
typical curve for absorption as shown in the figure.