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: , 2
(a) Since adsorption is exothermic process, as adsorption proceeds number of active sites present over adsorbent decreases, so less heat is evolved.
(b) Since $\mathrm{NH}_{3}$ has higher force of attraction on adsorbent due to its polar nature (high value of 'a').
(c) As the adsorption increases, residual forces over surface decreases.
(d) Since process is exothermic, on increasing temperature it shift to backward direction, so concentration of adsorbate particle decreases.