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प्रश्न
What is the role of adsorption in heterogenous catalysis?
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उत्तर
The role of heterogeneous catalysts can be explained in terms of adsorption of reactants on the surface of the catalyst.
The adsorption helps the reaction in the following ways:
(i) Adsorption increases the concentration of reactants on the surface of the catalyst. Due to increased concentration of the reactants, the reactions proceed rapidly.
(ii) Adsorbed molecules get dissociated to form active species like free radicals which react faster than molecules.
(iii) The adsorbed molecules are not free to move about and, therefore, they collide with other molecules on the surface.
(iv) The heat of adsorption evolved acts as energy of activation for the reaction (chemisorption).
Example: Adsorption of molecules of the reactant at the active site.
Occurrence of chemical reaction on the surface of catalyst
Desorption of product molecules
Example:
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संबंधित प्रश्न
Write the differences between physisorption and chemisorption with respect to the following:
(i) Specificity
(ii) Temperature dependence
(iii) Reversibility and
(iv) Enthalpy change
Give reasons for the following observations:
Physisorption decreases with increase in temperature.
Why is adsorption always exothermic?
Distinguish between the meaning of the terms adsorption and absorption. Give one example of.
What is the difference between physisorption and chemisorption?
Physisorption is reversible while chemisorption is irreversible. Why ?
Give reasons for the following observations :
Powdered substances are more effective adsorbents.
Which of the following compounds is formed when tungsten adsorbs oxygen gas?
Chromatography is based on the principle of ____________.
The extent of adsorption increases with the ____________.
Physical adsorption of a gaseous species may change to chemical adsorption with ______.
What is the role of activated charcoal in gas mask used in coal mines?
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
Assertion: Detergents with low CMC are more economical to use.
Reason: Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC.
Which among the following is a false statement?
In physical adsorption, gas molecules are bound on the solid surface by
Assertion A : Activated charcoal adsorbs SO2 more efficiently than CH4.
Reason R : Gases with lower critical temperatures are readily adsorbed by activated charcoal.
In light of the above statements, choose the correct answer from the options given below.
Which of the following statements is incorrect regarding physisorptions?
