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प्रश्न
Why is adsorption always exothermic?
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उत्तर
ΔH is always negative because during adsorption, the surface energy decreases in the form of heat. Furthermore, ΔS is negative because when a gas is adsorbed on a solid surface, its movement is restricted; this leads to a decrease in the entropy of the gas. Now, for a process to be spontaneous, ΔG should be negative.
∴ ΔG = ΔH − TΔS
Because ΔS is negative, TΔS becomes positive. Therefore, ΔH has to be highly negative for the spontaneous process to make ΔG negative. Hence, adsorption is always exothermic.
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
Write any two characteristics of chemisorption.
What is the difference between physisorption and chemisorption?
How does chemisorption vary with temperature?
Answer in one sentence:
Name type of adsorption in which vander Waals focres are present.
Which among the following is a property of physisorption?
Powdered substances are more effective adsorbents than their crystalline forms because ____________.
Which of the following is not a favourable condition for physical adsorption?
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) \[\ce{CH3COOCH3 (l) + H2O (l) ->[HCI(l)] CH3COOH (aq) + CH3OH (aq)}\]
Rate of physisorption increase with:-
