Adsorption of a gas on the surface of solid is sgenerally accompanied by decrease in entropy but still it is spontaneous in naturre. Explain.

Explanation

The molecules of adsorbate are held on the surface of adsorbent and therefore, they have lesser tendency to move freely. Therefore, its entropy decreases and `DeltaS` is -ve, which opposes the process. However, adsorption is an exothermic process and therefore, `DeltaH` is-ve. The magnitude of `DeltaH` is more than `T Delta S` so that
`DeltaG = DeltaH - T Delta S = (-) - T (-)`
if `DeltaH gt T Delta S, DeltaS = -ve`
Therefore, there is decrease in free energy and hence, it is a spontaneous process.