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Question
Give reasons for the following observations :
Powdered substances are more effective adsorbents.
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Solution
Adsorption is a surface phenomenon. Therefore, the process of adsorption is directly proportional to the surface area available for adsorption to take place. Both physisorption and chemisorption increase with an increase in the surface area. Powdered substances have large surface areas. Hence, powdered substances are more effective adsorbents.
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RELATED QUESTIONS
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.
How does chemisorption vary with temperature?
Adsorption increases when ____________.
Powdered substances are more effective adsorbents than their crystalline forms because ____________.
Extent of physisorption of a gas increases with ______.
Physical adsorption of a gaseous species may change to chemical adsorption with ______.
In which of the following reactions heterogenous catalysis is involved?
(a) \[\ce{2SO2 (g) + O2 (g) ->[NO(g)] 2SO3 (g)}\]
(b) \[\ce{2SO2 (g) ->[Pt(s)] 2SO3 (g)}\]
(c) \[\ce{N2 (g) + 3H2 (g) ->[Fe(s)] 2NH3 (g)}\]
(d) \[\ce{CH3COOCH3 (l) + H2O (l) ->[HCI(l)] CH3COOH (aq) + CH3OH (aq)}\]
Why is chemisorption referred to as activated adsorption?
Why do physisorption and chemisorption behave differently with rise in temperature?
