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Question:

Which one of the following characteristic is associated with adsorption?

△Gand△Hare negative but△Sis positive

△Gis negative but△Hand△Sare positive

△G, △Hand△Sall are negative

△Gand△Sare negative but△His positive

Solution:

For adsorption, △G, △H, and △S all are negative. Adsorption is a spontaneous process; therefore, the change in free energy for the process is negative. Since adsorption is exothermic in nature, the enthalpy change is negative. The entropy change is negative because the adhering of gas molecules to the surface lowers randomness.