Which one of the following characteristics is associated with adsorption ?

Options

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

Answer

B

Explanation

Adsorption is spontaneous process, therefore change in the free energy `(DeltaG)` for the process is negative. According to Gibbs.s Helmholtz egn.
`DeltaG`-`DeltaH-TDeltaS`
`DeltaS` is negative because adhering of gas molecules to the surface lowers the randomness.
`DeltaG` can be ve only when `DeltaH` is-ve.