Which one of the following characteristics is associated with adsorption ?

Options

A. `DeltaG and DeltaH` are negative but `DeltaS` is positive
B. `DeltaG and DeltaS` are negative but `DeltaH` is positive
C. `DeltaG` is negative but `DeltaHand DeltaS` are positive
D. `DeltaG, DeltaHand DeltaS` all are negative

Answer

D

Explanation

As the molecules of the adsorbate are held on the surface of the solid adsorbent, netropy decreases, i.e., `DeltaS` is -ve.
As adsorption is a spontaneous process, `DeltaG=-ve.`
Now as `DeltaG=DeltaH-T DeltaS` is -ve, `DeltaG` can be-ve only if `DeltaH` is -ve.