MCQ on Adsorption with Answers

Multiple Choice Questions on Adsorption

Here are a few MCQ on adsorption. Let us practise or solve them to understand how much we really know about Adsorption Isotherm.

Important Points to Remember about Adsorption

  1. Adsorption : The phenomenon of increase in concentration at the surface due to molecular surface force is known as adsorption. (ii) Adsorbate : The substances solids, gases or liquids which are adsorbed on the surface of adsorbent are called adsorbate. (iii) Adsorbent : The solid or liquid substance on the surface of which adsorption takes place is called adsorbent. Examples of adsorbents are activated charcoal, Pt, Pd, Ni, Silica gel, gelatin, Al2O3, starch. (iv) Absorption :When a substance is uniformly distributed throughout the body of a solid or liquid, the phenomenon is called absorption. (v) Sorption :It may be defined as the process in which both adsorption and absorption take place simultaneously.
  2. Adsorption is due to the fact that the surface particles of the adsorbent are in different state than the particles inside the bulk. Inside the adsorbent all the forces acting between the particles are mutually balanced but on the surface, particles are not surrounded by atoms or molecules on all sides and hence they possess unbalanced or residual attractive forces.
  3. Depending upon the nature of forces between molecules of adsorbate and adsorbent, adsorption is of two types Physical Adsorption and Chemical Adsorption. 
  4. The phenomenon of adsorption finds a number of applications. Important ones are listed here:
  5. (i) Gas masks :  Gas mask (a device which consists of activated charcoal or mixture of adsorbents) is usually used for breathing in coal mines to adsorb poisonous gases.
  6. (ii) Removal of colouring matter from solutions : Animal charcoal removes colours of solutions by adsorbing coloured impurities.
  7. (iii) Separation of inert gases : Due to the difference in degree of adsorption of gases by charcoal, a mixture of noble gases can be separated by adsorption on coconut charcoal at different temperatures.


MCQ on Adsorption Isotherm  : 

1. Physical adsorption is appreciable at__________

(1) Higher temperature 

(2) Lower temperature

(3) At room temperature 

(4) 1000°C

Answer: 2


2. Which characteristic of adsorption is wrong___________

(1) Physical adsorption in general decreases with temperature

(2) Physical adsorption in general increases with temperature

(3) Physical Adsorption is a reversible process

(4) Adsorption is limited to the surface only

Answer : 2


3. The rate of physical adsorption________

(1) Decreases with increase of pressure

(2) Is independent at high pressure

(3) Is maximum at one atmospheric pressure

(4) Always increases with increase of pressure

Answer: 2


4. Which of the following is not a characteristic of chemisorption__________

(1) Adsorption is irreversible

(2) DH is of the order of 40 kJ

(3) Adsorption is specific

(4) Adsorption increases with increase of surface area

Answer: 2


5. Sorption is the term used when_______

(1) Adsorption takes place

(2) Absorption takes place

(3) Both takes place

(4) Desorption takes place

Answer : 3


6. Which among the following statement is false_________

(1) The adsorption may be monolayered or multilayered

(2) Particle size of adsorbent will not affect the amount of adsorption 

(3) Increase of pressure increases amount of adsorption

(4) Increase of temperature may decrease the amount of adsorption

Answer: 2


7. Which of the following is not an adsorbent?

(1) Carbon

(2) Polymers and resins

(3) Clay

(4) Dry sponge

Answer: 4


8. The extent of adsorption of a gas on a solid depend on___________

(1) nature of gas

(2) pressure of gas

(3) temperature of the system

(4 )all of the mentioned

Answer: 4


9. In physical adsorption, the gas molecules are held on solid surface by_________

(1) Chemical forces

(2) Electrostatic forces

(3) Gravitational forces

(4) Vander Waal's forces

Answer: 4


10. Which one of the following is an example of adsorption?

(1) ammonia in contact with water

(2) anhydrous CaCl2 with water

(3) silica gel in contact with water vapours

(4) all of these

Answer: 3


11. Which of the following isotherm is applicable to physical adsorption?

(1) Langmuir

(2) BET

(3) Freundlich

(4) Kisluik

Answer: 3


12. Chemisorption__________

(1) Involves the weak attractive interactions between adsorbent and adsorbate 

(2) Is irreversible in nature

 (3) Decreases with increase of temperature

(4) Involves multilayer formation of adsorbent on adsorbate

Answer: 1


13. Which of the following statements regarding the physical adsorption of a gas on surface of solid is not correct?

(1) on increasing temperature, adsorption increases continuously

(2) enthalpy changes are negative

(3) adsorption is specific

(4) it is reversible in nature

Answer: 1


14. Pd can adsorb 900 times its volume of hydrogen. This is called ______

(1) Absorption

(2) Adsorption

(3) Occlusion

(4) 2 & 3 both

Answer : 4


15. Which is correct________

(1) Langmuir adsorption is highly specific

(2) vander-Waal's adsorption is reversible

(3) Both 1 & 2 are exothermic

(4) All are correct

Answer: 4


16. Adsorption is accompanied by________

(1) Decrease in entropy of the system

(2) Decrease in enthalpy of the system

(3) TDS for the process is negative

(4) All

Answer: 4


17. Which one of the following is not a correct statement ?

(1) Physical adsorption is reversible in nature

(2) Physical adsorption involves vander waals forces

(3) Rate of physical adsorption increases with increase of pressure on the adsorbate

(4) High activation energy is involved for physical adsorption

Answer: 4


18. The extent of adsorption of a gas on a solid depends on_______

(1) The nature of gas

(2) Pressure of gas

(3) Temperature of the system

(4) All

Answer: 4


19. Which forms multi molecular layers during adsorption________

(1) Physical adsorption

(2) vader Waal's adsorption

(3) Freundlich adsorption

(4) All

Answer : 4 


20. The Langmuir adsorption isotherm is deduced using the assumption.

(1) The adsorption sites are equivalent in their ability to adsorb the particles.

(2) The heat of adsorption varies with coverage.

(3) The adsorption molecules interact with each other.

(4) The adsorption takes place in multilayers

Answer : 1


21. Which of the following is incorrect for physi-sorption_________

(1) Reversible 

(2) Increases with increase in temperature

(3) Low heat of adsorption

(4) Increases with increase in surface area

Answer: 2


22. In Freundlich Adsorption isotherm, the value of 1/n is__________

(1) 1 in case of physical adsorption

(2) 1 in case of chemisorption

(3) between 0 and 1 in all cases

(4) between 2 and 4 in all cases

Answer : 3