Surface Chemistry
Q. In the context of adsorption, what does the term 'saturation' refer to?
A.
Complete coverage of the adsorbent surface
B.
Maximum temperature for adsorption
C.
Equilibrium state of adsorption and desorption
D.
None of the above
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Solution
Saturation refers to the complete coverage of the adsorbent surface by the adsorbate.
Correct Answer: A — Complete coverage of the adsorbent surface
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Q. In the Freundlich adsorption isotherm, which parameter indicates the extent of adsorption?
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Solution
In the Freundlich isotherm, K is the adsorption coefficient that indicates the extent of adsorption.
Correct Answer: A — K
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Q. In the Langmuir adsorption isotherm, what assumption is made about the adsorption sites?
A.
They are identical and have the same energy
B.
They are different and have varying energy
C.
They can accommodate multiple layers
D.
They are not limited in number
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Solution
The Langmuir isotherm assumes that all adsorption sites are identical and have the same energy.
Correct Answer: A — They are identical and have the same energy
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Q. In the Langmuir adsorption isotherm, what does the term 'b' represent?
A.
Adsorption energy
B.
Surface area
C.
Equilibrium constant
D.
Adsorption capacity
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Solution
'b' in the Langmuir isotherm represents the equilibrium constant related to the adsorption process.
Correct Answer: C — Equilibrium constant
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Q. The Freundlich adsorption isotherm is applicable to which type of adsorption?
A.
Physisorption only
B.
Chemisorption only
C.
Both physisorption and chemisorption
D.
None of the above
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Solution
The Freundlich isotherm can describe both physisorption and chemisorption processes.
Correct Answer: C — Both physisorption and chemisorption
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Q. The Langmuir adsorption isotherm assumes that:
A.
Adsorption occurs on a surface with infinite sites
B.
Adsorption sites are equivalent
C.
Adsorption is a multilayer process
D.
Adsorption is independent of pressure
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Solution
The Langmuir isotherm assumes that adsorption sites are equivalent and that the process is monolayer.
Correct Answer: B — Adsorption sites are equivalent
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Q. The Langmuir adsorption isotherm assumes which of the following?
A.
Adsorption occurs on a surface with infinite sites
B.
Adsorption sites are equivalent
C.
Adsorption is a multilayer process
D.
Adsorption is temperature independent
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Solution
The Langmuir isotherm assumes that adsorption occurs on a surface with a finite number of equivalent sites.
Correct Answer: B — Adsorption sites are equivalent
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Q. What is the effect of increasing temperature on physisorption?
A.
Increases adsorption
B.
Decreases adsorption
C.
No effect
D.
Depends on the adsorbate
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Solution
Increasing temperature generally decreases physisorption because it disrupts the weak van der Waals forces.
Correct Answer: B — Decreases adsorption
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Q. What is the main characteristic of a catalyst in surface chemistry?
A.
It increases the rate of reaction by changing the equilibrium.
B.
It is consumed in the reaction.
C.
It provides an alternative reaction pathway.
D.
It decreases the activation energy of the reaction.
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Solution
A catalyst provides an alternative reaction pathway, which lowers the activation energy and increases the reaction rate.
Correct Answer: C — It provides an alternative reaction pathway.
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Q. What is the main characteristic of a catalyst in surface reactions?
A.
It is consumed in the reaction.
B.
It lowers the activation energy.
C.
It increases the temperature of the reaction.
D.
It changes the equilibrium constant.
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Solution
A catalyst lowers the activation energy of a reaction without being consumed in the process.
Correct Answer: B — It lowers the activation energy.
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Q. What is the main difference between adsorption and absorption?
A.
Adsorption involves a surface phenomenon
B.
Absorption is a surface phenomenon
C.
Both are the same
D.
Adsorption is faster than absorption
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Solution
Adsorption is a surface phenomenon, while absorption involves the entire volume of the material.
Correct Answer: A — Adsorption involves a surface phenomenon
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Q. What is the main difference between physisorption and chemisorption?
A.
Temperature dependence
B.
Nature of forces involved
C.
Reversibility
D.
All of the above
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Solution
The main difference lies in the nature of forces involved; physisorption is due to weak van der Waals forces, while chemisorption involves strong chemical bonds.
Correct Answer: D — All of the above
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Q. What is the primary driving force for adsorption in physisorption?
A.
Chemical bonds
B.
Van der Waals forces
C.
Hydrogen bonds
D.
Ionic interactions
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Solution
Physisorption is primarily driven by weak van der Waals forces.
Correct Answer: B — Van der Waals forces
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Q. What is the primary factor that affects the rate of adsorption of a gas on a solid surface?
A.
Temperature
B.
Pressure
C.
Surface area of the adsorbent
D.
Nature of the gas
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Solution
The rate of adsorption is primarily affected by the surface area of the adsorbent, as a larger surface area provides more sites for adsorption.
Correct Answer: C — Surface area of the adsorbent
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Q. What is the primary mechanism of adsorption in physisorption?
A.
Chemical bonding
B.
Van der Waals forces
C.
Hydrogen bonding
D.
Ionic bonding
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Solution
Physisorption occurs primarily due to weak Van der Waals forces.
Correct Answer: B — Van der Waals forces
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Q. What is the primary process involved in the adsorption of gases on solid surfaces?
A.
Diffusion
B.
Condensation
C.
Chemical reaction
D.
Van der Waals forces
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Solution
Adsorption of gases on solid surfaces primarily occurs due to Van der Waals forces, which are weak intermolecular forces.
Correct Answer: D — Van der Waals forces
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Q. What is the role of activated charcoal in adsorption processes?
A.
Catalyst
B.
Adsorbent
C.
Solvent
D.
Reagent
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Solution
Activated charcoal is commonly used as an adsorbent due to its high surface area and porosity.
Correct Answer: B — Adsorbent
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Q. What is the significance of the BET theory in surface chemistry?
A.
Describes physisorption
B.
Describes chemisorption
C.
Determines surface area of solids
D.
Calculates adsorption energy
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Solution
The BET theory is significant for determining the surface area of solids based on multilayer adsorption.
Correct Answer: C — Determines surface area of solids
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Q. What is the term for the process of removing adsorbed molecules from a surface?
A.
Absorption
B.
Desorption
C.
Sorption
D.
Adsorption
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Solution
Desorption is the process of removing adsorbed molecules from a surface.
Correct Answer: B — Desorption
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Q. What is the term for the process where a gas or liquid forms a thin layer on a solid surface?
A.
Absorption
B.
Desorption
C.
Adsorption
D.
Sorption
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Solution
Adsorption is the process where a gas or liquid forms a thin layer on a solid surface.
Correct Answer: C — Adsorption
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Q. What is the term used for the amount of solute that can be adsorbed per unit mass of adsorbent?
A.
Adsorption isotherm
B.
Adsorption capacity
C.
Adsorption efficiency
D.
Adsorption rate
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Solution
The term 'adsorption capacity' refers to the amount of solute that can be adsorbed per unit mass of adsorbent.
Correct Answer: B — Adsorption capacity
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Q. What type of adsorption occurs when the adsorbate forms strong chemical bonds with the adsorbent?
A.
Physisorption
B.
Chemisorption
C.
Desorption
D.
Sorption
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Solution
Chemisorption involves the formation of strong chemical bonds between the adsorbate and the adsorbent.
Correct Answer: B — Chemisorption
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Q. What type of isotherm is represented by the Freundlich equation?
A.
Langmuir isotherm
B.
BET isotherm
C.
Freundlich isotherm
D.
Temkin isotherm
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Solution
The Freundlich equation describes a type of adsorption isotherm that is applicable to heterogeneous surfaces.
Correct Answer: C — Freundlich isotherm
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Q. Which is the correct order of adsorption strength from highest to lowest?
A.
Physisorption > Chemisorption
B.
Chemisorption > Physisorption
C.
Physisorption = Chemisorption
D.
None of the above
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Solution
Chemisorption is stronger than physisorption due to the formation of chemical bonds.
Correct Answer: B — Chemisorption > Physisorption
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Q. Which of the following factors does NOT affect the adsorption capacity of a solid?
A.
Surface area
B.
Temperature
C.
Nature of the adsorbate
D.
Color of the adsorbent
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Solution
The color of the adsorbent does not affect its adsorption capacity; factors like surface area, temperature, and nature of the adsorbate do.
Correct Answer: D — Color of the adsorbent
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Q. Which of the following factors does NOT affect the adsorption of a gas on a solid?
A.
Temperature
B.
Pressure
C.
Surface area of the solid
D.
Color of the solid
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Solution
The color of the solid does not affect the adsorption of a gas; however, temperature, pressure, and surface area do.
Correct Answer: D — Color of the solid
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Q. Which of the following factors does NOT affect the adsorption of gases on solids?
A.
Temperature
B.
Pressure
C.
Surface area of adsorbent
D.
Color of the adsorbent
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Solution
The color of the adsorbent does not affect the adsorption process; however, temperature, pressure, and surface area do.
Correct Answer: D — Color of the adsorbent
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Q. Which of the following factors does NOT affect the adsorption process?
A.
Temperature
B.
Surface area of adsorbent
C.
Nature of adsorbate
D.
Color of adsorbent
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Solution
The color of the adsorbent does not affect the adsorption process; factors like temperature, surface area, and nature of adsorbate do.
Correct Answer: D — Color of adsorbent
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Q. Which of the following factors does NOT affect the rate of adsorption?
A.
Surface area of adsorbent
B.
Temperature
C.
Pressure of gas
D.
Color of adsorbent
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Solution
The color of the adsorbent does not affect the rate of adsorption.
Correct Answer: D — Color of adsorbent
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Q. Which of the following is a characteristic of adsorption isotherms?
A.
They describe the relationship between pressure and volume.
B.
They describe the relationship between concentration and temperature.
C.
They describe the relationship between the amount of adsorbate and pressure at constant temperature.
D.
They describe the relationship between the amount of adsorbate and the surface area.
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Solution
Adsorption isotherms describe the relationship between the amount of adsorbate and pressure at constant temperature.
Correct Answer: C — They describe the relationship between the amount of adsorbate and pressure at constant temperature.
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