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KCET2012ChemistryThermodynamics (C)

During the adsorption of a gas on the surface of a solid, which of the following is true?

Options

  1. AG >0, H < 0, S < 0
  2. BG < 0, H < 0, S < 0
  3. CG 0
  4. DG 0, S < 0

Correct answer

B. G < 0, H < 0, S < 0

Step-by-step solution

During the adsorption of a gas on the surface of a solid there is decrease in surface energy, i.e., it is an exothermic process. Therefore, H < 0 . Again when a gas is adsorbed, the freedom of movement of its molecules becomes restricted. This leads to decrease in the entropy of the gas after adsorption. Therefore, S < 0 . From equation, G = H - T S , G can be negative if process is spontaneous. Since, adsorption process is a spontaneous process, therefore, G < 0 .

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