Amongst the following statements regarding adsorption, those that are valid are :
(a) $\Delta \mathrm{H}$ becomes less negative as adsorption proceeds.
(b) On a given adsorbent, ammonia is adsorbed more than nitrogen gas.
(c) On adsorption, the residual force acting along the surface of the adsorbent increases.
(d) With increase in temperature, the equilibrium concentration of adsorbate increases.
Correct Option: , 3
(i) When gas is adsorbed on metal surface, $\Delta \mathrm{H}$ becomes less negative with progress of adsorption.
(ii) The gas having greater value of critical temperature $\left(\mathrm{T}_{\mathrm{C}}\right)$ is adsorbed more compared to lower $\mathrm{T}_{\mathrm{C}}$ containing gases. As $\mathrm{T}_{\mathrm{C}}\left(\mathrm{NH}_{3}\right)>\mathrm{T}_{\mathrm{C}}\left(\mathrm{N}_{2}\right)$, so $\mathrm{NH}_{3}$ is adsorbed more than $\mathrm{N}_{2}$ gas.