Question

Which one of the following characteristics is associated with adsorption?

(a) $\Delta G$ and $\Delta H$ are negative buit $\Delta S$ is positive.

(b) $\Delta G$ and $\Delta S$ are negative but $\Delta H$ is positive.

(c) $\Delta G$ is negative but $\Delta H$ and $\Delta S$ are positive.

(d) $\Delta G, \Delta H$ and $\Delta S$ all are negative.

Answer 1

Correct Option : (D)

Explanation :

As the molecules of the adsorbate are held on the surface of the solid adsorbent, entropy decreases i.e., $\Delta S=-$ ve.

As $\Delta G=\Delta H-T \Delta S$

For the adsorption to occur, $\Delta G=-v e$ and it is possible only if $\Delta H=-{ve}$.