Adsorption Basics and Factors Affecting Adsorption
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Adsorption Basics and Factors Affecting Adsorption

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Questions and Answers

What is a characteristic of physical adsorption?

  • It has a high enthalpy of adsorption.
  • It occurs slowly and is irreversible.
  • It forms a mono-layered adsorbate layer.
  • It is weak and highly reversible. (correct)

    • How does the temperature affect chemical adsorption?

  • It has no effect on adsorption.
  • It only occurs at low temperatures.
  • It increases with a rise in temperature. (correct)
  • It decreases with a rise in temperature.

    • What type of adsorbate layer is formed in physical adsorption?

  • Multi-layered layer at high pressure. (correct)
  • Layer consisting of strongly bonded molecules.
  • Mono-layered layer.
  • Irreversible layer.

    • What describes competitive adsorption?

    <p>A strongly adsorbed substance may displace a weakly adsorbed one.</p> Signup and view all the answers

    Which gas is least likely to be adsorbed due to its low critical temperature?

    <p>H2</p> Signup and view all the answers

    What is a key factor affecting the extent of adsorption?

    <p>Type of adsorbent surface available.</p> Signup and view all the answers

    What indicates the strength of chemical adsorption compared to physical adsorption?

    <p>Chemical adsorption has a higher energy of activation.</p> Signup and view all the answers

    Which condition is typically required for physical adsorption to occur more effectively?

    <p>More easily liquefiable gases.</p> Signup and view all the answers

    What happens to the extent of adsorption with an increase in gas pressure?

    <p>It increases until reaching a maximum at saturation pressure.</p> Signup and view all the answers

    Which statement best describes the effect of temperature on physical adsorption?

    <p>It decreases continuously with increase in temperature.</p> Signup and view all the answers

    What method is NOT mentioned as a way to activate metallic adsorbents?

    <p>Heating at high temperatures.</p> Signup and view all the answers

    Which type of adsorption is characterized by an initial increase followed by a decrease when temperature rises?

    <p>Chemisorption.</p> Signup and view all the answers

    To enhance the adsorbing power of an adsorbent, what physical change is suggested?

    <p>Sub-dividing the adsorbent into smaller pieces.</p> Signup and view all the answers

    What is the term for the graph that represents the relationship between the degree of adsorption and temperature at a constant pressure?

    <p>Adsorption Isobar.</p> Signup and view all the answers

    Which gases are generally adsorbed on finely divided transition metals such as Ni and Co?

    <p>H2, N2, and O2.</p> Signup and view all the answers

    What principle explains the desorption process when temperature is increased?

    <p>Le Chatelier's principle.</p> Signup and view all the answers

    What primarily differentiates absorption from adsorption?

    <p>Absorption occurs at a uniform rate while adsorption is a fast process.</p> Signup and view all the answers

    Which statement is true regarding the thermodynamics of adsorption?

    <p>During adsorption, heat is released, resulting in a negative change in enthalpy.</p> Signup and view all the answers

    How does temperature affect the adsorption process?

    <p>Decreasing temperature generally promotes adsorption due to lowered entropy.</p> Signup and view all the answers

    What is the primary force involved in physical adsorption?

    <p>Van der Waals forces</p> Signup and view all the answers

    What is competitive adsorption?

    <p>When different adsorbates compete for the same adsorption sites on an adsorbent.</p> Signup and view all the answers

    Which factor does NOT affect the rate of adsorption?

    <p>Shape of the adsorption site on the adsorbent</p> Signup and view all the answers

    Which type of adsorption involves strong chemical bonds?

    <p>Chemisorption</p> Signup and view all the answers

    What happens to enthalpy as adsorption approaches equilibrium?

    <p>Enthalpy becomes less negative until it equals T AS.</p> Signup and view all the answers

    Study Notes

    Physical Adsorption Characteristics

    • Physical adsorption is characterized by weak van der Waals forces between the adsorbate and the adsorbent.
    • A multimolecular layer of adsorbate is formed in physical adsorption.

    Chemical Adsorption and Temperature

    • Chemical adsorption is favored at lower temperatures.
    • Increasing temperature generally reduces the extent of chemical adsorption due to the breaking of chemical bonds.

    Competitive Adsorption

    • Competitive adsorption occurs when multiple adsorbates compete for the same adsorption sites on the adsorbent.
    • The adsorbate with the stronger affinity for the adsorbent will be adsorbed preferentially.

    Adsorption and Critical Temperature

    • Gases with low critical temperatures, such as helium (He), are less likely to be adsorbed due to their weak intermolecular forces.

    Factors Affecting Adsorption

    • The extent of adsorption is significantly affected by the surface area of the adsorbent.
    • Higher surface area leads to greater adsorption capacity.

    Distinguishing Adsorption Types

    • Chemical adsorption is characterized by a higher enthalpy change compared to physical adsorption, indicating stronger interactions.

    Conditions for Adsorption

    • Physical adsorption is more effective at lower temperatures.

    Pressure and Adsorption

    • Increasing gas pressure generally increases the extent of adsorption.

    Temperature and Physical Adsorption

    • Physical adsorption is an exothermic process, meaning it is favored at lower temperatures.

    Activation of Metallic Adsorbents

    • Methods to activate metallic adsorbents include crushing, grinding, and increasing the surface area.
    • Heating is NOT mentioned as a method for activating metallic adsorbents.

    Temperature and Adsorption

    • Chemical adsorption exhibits a unique relationship with temperature, initially increasing and then decreasing as temperature rises.

    Enhancing Adsorbent Power

    • To enhance the adsorbing power of an adsorbent, increasing its surface area is generally suggested through methods like crushing or grinding.

    Adsorption Isotherm

    • The relationship between the degree of adsorption and temperature at a constant pressure is represented by an adsorption isotherm.

    Adsorbents and Gases

    • Finely divided transition metals like nickel (Ni) and cobalt (Co) are commonly used to adsorb gases like hydrogen (H2) and carbon monoxide (CO).

    Desorption and Temperature

    • Increasing the temperature promotes desorption due to weakening the adsorbate-adsorbent interactions.

    Distinguishing Adsorption and Absorption

    • Absorption involves the penetration of the adsorbate INTO the bulk of the adsorbent.
    • Adsorption involves the accumulation of the adsorbate ON the surface of the adsorbent.

    Thermodynamics of Adsorption

    • Adsorption is generally an exothermic process, meaning it releases heat.
    • The entropy change during adsorption is typically negative, as the adsorbate becomes more ordered on the surface.

    Temperature and Adsorption Process

    • Lower temperatures generally favor adsorption.

    Forces in Physical Adsorption

    • The primary force involved in physical adsorption is the van der Waals force.

    Competitive Adsorption

    • Competitive adsorption occurs when multiple adsorbates compete for the same available adsorption sites on the adsorbent.

    Factors Affecting Adsorption Rate

    • Factors affecting the rate of adsorption include:
      • Temperature
      • Pressure
      • Surface area of the adsorbent
      • Concentration of the adsorbate
      • The nature of the adsorbent and adsorbate
    • The shape of the adsorbent does NOT affect the rate of adsorption

    Chemical Adsorption

    • Chemical adsorption involves the formation of strong chemical bonds between the adsorbate and adsorbent.

    Enthalpy and Equilibrium

    • As adsorption approaches equilibrium, the enthalpy change approaches zero.

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    Description

    Explore the fundamental concepts of adsorption, including the differences between physical and chemical adsorption. This quiz delves into factors influencing adsorption efficiency such as the nature of gases and adsorbents. Test your understanding of these essential principles in the field of chemistry.

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